I know 'video game' gets tossed around like a pejorative, but the sad reality is that it's a market & a medium that is just vastly larger than that of TTRPGs, so more folks of higher paygrades burn out more brain cells pondering the imponderables of designing them - and, sometimes, there are valid insights to be gained from what they come up with that can be gleaned by the TTRPG hobby. Because TTRPGs don't rate the resources to come up with those sorts of things on their own.
Not intended as a pejorative, really... did it come off that way, or did you read it that way due to other conversations you've had? I love video games, and a couple of friends of mine are in video game design. I also played more 3e and 4e than all of the oldschool editions combined, by a wide margin.
That said, video game design, particularly the design that strives to create a sweet spot treadmill, is optimizing for a different thing than TTRPGs are.
And they lack a fundamental asset that TTRPGs have. Video games need to work without a human referee/dictator/overlord driving them.
Hopefully it's still fundamentally the same game in some sense.

But the assumption is presumably that the game would still work at all levels (work the same or work differently, but work)...
I think it works, but the play experience changes.
It'd be a faulty assumption for almost every edition, sure.
Or just the middle of the 'Companion' levels in BECMI... As variously problematic and/or disappointing as capstones can be, it may well be sooner. I'm not sure the last few levels are even meant to be played. Or, rather, I suspect that they're designed with the idea that the fun of playing those levels won't come from the mechanics read off the class advancement table.
Sure... is the fun of playing
any level primarily coming from the mechanics on the class advancement table? I wouldn't say so...
So BA simply can't deliver 'level appropriate encounters?' That approach to play constitutes an un-supported style?
No, that's not what I said at all. Bounded Accuracy can easily deliver level appropriate encounters... but it perhaps can't easily do so if you assume all of the following:
1: Straight up fight without substantial battlefield control, mobility, and tactical acumen executed by the DM.
2: Fight is with an individual monster
3: Monster is PartyLevel+X=CR where X is a static number (e.g. 2)
If number 1 is violated, so it's not a straight up slugfest, then all bets are off.
If number 2 is violated, creating a difficult, challenge is pretty easy.
Number 3 is mostly what I have been opining on. I think, for the classic "solo" monster, you are chasing a proverbial dragon. You can't use a rule that works at level 1 (e.g. Party level+2 CR) and expect it to work at level 15. The increase in CR required to maintain the "solo" feel will go up at a faster rate than the party's level will.
BA isn't that big a change. It's just making some factors smaller on both sides of an equation, really. It has ripple effects, though...
I disagree immensely.
Bounded Accuracy does a decent job of recreating the best D&D edition ever (3.5 E6) in a more traditional, player friendly 1-20 package.
And it can easily be dragged even further into an E6 style of game, without actually implementing E6. The core mechanics of 5e are so well suited to this style of play that the number of modular changes to really nail it are relatively small, and all of them feel natural and fitting within the 5e framework. For example, some of the truly superb low magic suggestions you yourself made in another thread (either dropping spell slots or dropping spells known, for different tones that achieve similar overall results)