How so? The OEMs want to make hardware that runs Windows. Microsoft provides a specification[0] and certification suites[1] that defines what "Windows-compatible" means, which OEMs then follow. Nothing coercive about that.

There is no open standard that defines what a PC is. Linux and other operating systems are piggybacking on the Windows PC standard. If they want OEMs to manufacture hardware to their standards, they'll have to create their own "Linux-compatible" specification and persuade OEMs to follow it.

[0] https://msdn.microsoft.com/windows/hardware/commercialize/de...

[1] https://msdn.microsoft.com/en-us/library/windows/hardware/dn...