Unity doesn't really use Unity Engine, they don't ship a game with it or use it in the real world.
From what someone on HN has described before last time they showed something off like this, even if it's made internally at Unity it isn't really made with the tools you get downloading Unity yourself, it's made by an offshoot team who has people doing changes to the internals of the engine and writing custom hacks for this one use case. Then they ship the video, be it Adam (2016) or Enemies (2022) but then that's it, they go on to work on something else and the tweaks and tooling never get made into something viable for the main engine.
That's why Unity themselves managed to ship Adam [1] 7 years ago but since no one else has used Unity to create content like that since. Feels like it's almost to a yearly schedule now where Unity will do a PR demo like the link above on this topic and then nothing real ever materializes.
[1] https://www.youtube.com/watch?v=GXI0l3yqBrA