That's the most infuriating thing about it.People are surprisingly blind to this shit. All MS needs to do is make DirectX progressively worse on Win10 for Win32 to enable a lot of the shit that is being discussed in the OP.
That doesn't mess with vast majority of their Corp customers but will make gaming on non UWP platforms (GoG, Steam, Origin, Ubisoft, etc...) progressively worse. And yes, MS can deprecate older APIs.
As far as competitors MS have done this to? There are many in the business line Netscape, Novell, etc... MS is notorious for taking public APIs and making them just enough different for 3rd party shit not to work or work badly. Heck, Kerberos is a good example that wasn't truly fixed till Server 2008 R2 I think. Even now they take SAML 2.0 and put some proprietary shit in their ADFS model.
So yeah, I can absolutely see MS trying to pull this one. It would really be targetting closed system Apple-Google like model with UWP. Gaming would be just a drive by.
Inconveniencing gamers on Windows and actively endangering the future of unrestricted modding and preservation of games is one thing. Doing so to prop up your failing business in completely different sectors is something else.