This makes no sense either. This isn't a level or anything at all, it's literally just Sonic moving around and jumping. this is just a demonstration of how Sonic would move around. The "level" even if "fully textured" isn't even a level. It's literally nothing, it's just physically a space, an empty space with no logic, no "obstacle" or anything. Saying it looks like a Mario 64 clone doesn't make sense because Mario 64 is a complete game, this isn't even a level yet.
From the YT video itself:
Q: Some other features are missing (e.g. Jump Pads, Vaulting)...What happened to them?
A: Most "missing" features are scrapped.
Q: Is this an "engine"?
A: No...For now...Well at this point I'm not even sure what it is or isn't. Seems to me like an amalgamation of mechanics and features that have little reason to even be there, as well as little relation and contribution to each other.
Q: Are you going to disappear again? A: Nope... I'll try to post stuff more frequently.
Q: When can we expect a release?
A: When I manage to make an actual stage.
Q: Wait...is that it? I'm underwhelmed...
A: Have you even bothered to stick 'till the end?
This isn't even a stage lol.