Kind of, it is a problem for the developers that write their own engines, instead of using middleware.

For the middleware companies, it isn't a problem to write multiple backends, as it is the reason why they exist in first place.

Also OpenGL never had much use in the consoles, for example.

However, it just goes to show that company X will do Y, because they sit in some Y organization isn't given.

No, it is Apple back to being itself.

The old Apple was even more proprietary than Microsoft was.

All hardware and software were Apple specific.