I suspect if they let steam do it there is nothing stopping steam from running it on Linux as well, provided the usual compatibility features such as proton wouldnt be deliberately incapacitated by Microsoft; which in turn would piss off valve a lot because of the steam deck and OS.
They invested heavily in their Linux fork and compatibility suite, if windows store were to fuck with that I suspect they would be on the losing end. Steam users are very loyal to the company and by default extremely hostile to proprietary fuckery.