I’m becoming less sure of this, but let me explain.
Now I actually tend to use the number 5 and sometimes even 7 rather than 3 because there is stuff going below the level of adult human that is sometimes worth talking about, but if we take our starting point as adult humans and their naive perspectives then I think 3 is fine.
So what I’ve thought for a long time is that at 3 we get enough to form stable loops that short circuit the need for more levels. You give one of my favorite examples of this in your piece—thesis, antithesis, synthesis—which forms a loop and doesn’t require more oscillations because you can just make the synthesis the new thesis and repeat to refine without needing to see deeper. Some folks around here know this as the “you don’t need more than 3 levels of recursion” heuristic.
However there are times when you may want to manipulate the loop itself while also working on it at the object level. I sometimes find myself wandering in this direction during meditation but find it hard to do because it’s asking me to keep a lot of stuff in working memory at once. It may turn out that I can’t actually do it or take advantage of another oscillation/level/etc., but I do find myself wandering that way. This is not to dispute that 3 is not enough, only that having more may enable experiences that would otherwise be too complex to have without the aid of memory.