Graphics APIs have trended to be lower level, running basically directly on the GPU. I doubt Microsoft will be able to convince game developers to go the other way just to get their fingers inbetween you and your game.
Microsoft has been absolute dogshit at releasing newer program APIs for developer to use. Wine doesn't support UWPs/appx just because there's no demand, since no-one uses the Windows Store. You expect that same Microsoft to get game devs to jump on their new DRM scheme?
Microsoft released even their darling Halo in 2020 and 2021, and have committed to release Halo: Campaign Evolved in 2026 on Steam. I can't think of any new titles under the Microsoft umbrella that hasn't also released in Steam. They've realised that battle is lost. They can change course, but that doesn't mean they'll get anything out of that.
Developers are already doing sanity checks and patches specific to SteamOS. That trend will continue if SteamOS or Linux gains ground. It doesn't matter that the foundation is Microsoft, because even if Microsoft goes bankrupt tomorrow, that foundation doesn't disappear, and even the most malicious Microsoft can't unmake reimplementations or translation layers of their APIs.
That same studio would prefer to make a stable Windows version than an unstable Linux version that might not even work in 5 years since it used some stupid dependency. ANd if they're sensible about it and do a sanity check with Proton, Valve doesn't even have to do any work for them outside of what's already been done.