I agree that the question is where the problem happens.
I truly believe that I have and do experience things during RV sessions that are absolutely unique to my experience. Pretty regularly even on mundane targets. As well as occasional metaphysical stuff that I'm pretty certain really IS unique in my experience.
In fact I feel this is so pronounced that there is a good deal of experience I cannot convey because I just can't even bring it to the verbal/sketch level to do so. That's sort of a separate subject too about 'passive data' and the diff between doubleblind and post-feedback which I think is huge for these reasons.
But even of what I experience, yes my brain has to have some form of 'model' for something in order to put it into words. However it's like if a tall totally unique alien walked up to us at the grocery tomorrow. Assuming we did not mistake it for our teenage daughter (...you can tell I have one...), we still COULD perceive it. But yes, it WOULD require we use existing information in our brain to say, "The tentatacles are vaguely octopus-ish, and the eye-stalks remind me of chiquata bugs, and..." -- sure, every element we 'noticed' would be 'comparative' to something in our mental database for definition -- but that would not be saying that "we could only perceive what we already knew," that would merely be saying "we could only communicate what we perceive (even if it's novel) with the frameworks we've got for communications, which are based on what we already know".
Which is pretty much what others have said above I guess (I love the chinaman ref -- that used to be a common analogy -- but one I haven't heard in years!). (Someday someone is going to show up and go, "I'm that chinaman. You've been talking about me, yes?")
I have had experiences where I literally could not fully consciously perceive a good % of something, someone, and some place, and I knew even at the time it was because it was just flat out "too novel" -- that I was totally aware on a "lower level" but the top-level where my conscious mind is just couldn't touch it.
They say that babies have to experience things multiple times before their brains can "hold the pattern" -- like it has to wear a neural groove first or something, enough to be recognized -- I think a lot of experience in viewing suffers that 'not having an existing neural groove for this experience' -- not necessarily because the target data is ineffable, just because the way we're getting the information is so new, we have a lifetime of getting info consciously via the body but a much shorter time of getting info consciously 'through the inside'.
If I've been viewing off and on for 13 years think about it, let's say I spent 5 hours a week on it -- which is SO much more than I have by a mile LOL since I have long periods yearly where I'm not viewing -- I still have to break that down. 5 hours a week, 52 weeks a year is 260 hours. Times 13 years is 3380 hours. There's 8760 hours in a year so that means that in 'viewing time' of my "practice at perceiving in that manner and communicating it", I am like 5 months old. Compared to being 43 years old it's no wonder I'm less good at describing things via RV than I am at describing stuff I experience 'in regular life'.
Now, there is a separate but related topic here, which is that a lot of information I get in session literally IS what amounts to "a memory flash" of something that is not THE target, but rather, is ABOUT or LIKE the target. I believe this is part of where the idea that "we only get data we've already experienced" comes from. This is a BIG part of viewing -- the majority for me -- it's just not the 'only' kind of perception I get.
For example on the memory-based stuff, I get a flash of a green metal bridge near my childhood home town. I get a later flash of a green ornate decorative porch railing in the french quarter of new orleans that I saw in a picture. I have a separate flash of a thin walking path, dirt with stones along the sides. It turns out the target is a bridge, it's metal, it's green, but the metal is much much thinner than the other bridge, and the railing is thin like the N.O. railing thing, and it's a footbridge, a real thin one like that path. This is an example of getting data 'like/about' a target that is based on "existing personal experience" rather than merely getting the data directly. (I also got that the architect "loved it" literally.)
Sometimes I think that we get combinations that AVOID what we actually 'know' in favor of giving us something different because it has energetic elements the target does. For example in an old blog post I griped about how I'd gotten this great visual from above of a beach or bay edge, and this long walkway that went over the water, and at both ends there was this square wooden beam docklike area, and a guy walking down it which I suspected was NOT the target, just something 'about' it, but I also had this vague overlay of 'walk on water'.
Turns out it was a wooden porch leading up to a church door, voting going on there. Now despite there were various elements I could put together, the fact is I have *personally experienced* god knows how many wooden porches in my life -- even those leading up to churches! -- so why the heck the whole path across the water and 'walking on water' in the data coming through?! So:
I mused (who really knows) that (a) maybe the walk on water related to the church nature, as well as to the political nature of the voting going on there (having a hero, w-o-w as slang), and (b) for all I know -- god, who knows?! -- maybe the porch was literally built to keep the locals out of the water/mud every time it rained or something. What I'm saying is that MAYBE, when we try to figure out WHY we get the data we do, MAYBE the target has its OWN identity of a sort -- and maybe its "founding intent/reason for being" and its "construction" and its "physical nature" and its "actual usage" as well as its "general relationship to our species" (eg when we get myth/archetypal refs) -- maybe all of these things go into making a 'target' a somewhat larger and deeper identity.
To us, we don't give a damn -- we want to know the "shallow surface details" and don't bother me with the deeper details -- oh except when I need them -- oh except when they matter -- otherwise just tell me what it looks like on the surface to a bipedal mammal in this frequency please -- I wonder if the subconscious self is ever just exasperated LOL!
(A separate annoying question is, 'so which part matters? I can't judge without analysis, but if I don't make a decision and communicate promptly, I will be here 15 minutes detailing everything about a micro-second flash of something that probably has only about .05% to do with the target anyway, and likely sending myself into major aol drive on all the elements completely unrelated. So one actually DOES have to make an 'analytical decision' about 'what matters' during RV -- constantly in fact -- something that for some reason is like the elephant in the living room in this field since we all know you "can't analyze!" during session, but IMO that happens naturally as a result of any communication. Much like there is no such thing IMO as truly "raw data" -- 'door' and 'flat' and 'brown' are IMO no more raw than 'door' as long as they all came to me directly (vs. my mind having to consciously construct 'door' out of the other three, no matter how quickly). Might be I just know 'door' at a level well enough to be at the same perception point as those other things are. I grew up around Sage bushes in southern coastal california, a bit east of the beach in Ojai, and Sage is the only plant I have pointedly picked up in viewing sessions -- not as a smell or name but literally it just comes through like a 'raw data' base, the way 'water' might.)