Sure you can. That said, I'm not sure what Apple's usual style is and it might be pretty out of character (or not) to drop support shortly after an MR.
No you can't. Upstreaming a large feature like this requires at the very least allocating a number of manweeks to the upstreaming process, and that's without accounting for actually writing the feature in the first place. Making a PR and not following up would be worse PR (heh) than doing nothing, which is also costly.
If they had dumped a tarball or a fork somewhere with a hacked up PoC it could have looked like they just dumped what they had, but even that requires approvals and time from legal, and so someone has to decide its worth investing in.
(I have no interest in speculating about the Vision lineup itself, just commentating on open source contributions.)
You really don't understand how much money Apple's sunk on this and how little comparatively it takes to wind down operations in a way that makes partners and suppliers happy. Keeping a couple small teams going, even with entirely new versions shipping, to keep your supply chain whole and your partners coming back for future products is cheap and easy and very likely what Apple's doing now that most of the top talent was moved to spectacles and Siri. Letting your OS and partner software teams clear their pipelines is absolutely common at Apple and elsewhere. Denying that is silly.
They could also throw money out their window, light it on fire, let their employees do whatever they want instead of regular Apple work, etc.
A lot of managers (and legal) have to approve and allocate significant budget to bad ideas. Companies generally try to avoid doing bad ideas that are a net negative.
