Every major open source project is in no small way driven by the interests of corporate users, from which a non-trivial number of PR's and contributions come from. This is true from Linux and Postgres to Rust and Java.

Of course Microsoft only include functionality they want. Just like any other platform only include what they want. It is entirely their prerogative. Just because they don't include anything and everything other people want, it does not make them less open source.

We are entirely free to fork the project, embed the change and compile our own binaries. You don't have to strongarm a change into upstream for that.

Any non-trivial OSS project has corporate sponsors on the steering committee and feature set/fixes are mostly driven by these corporate sponsors. So in the end it's all same.