Yeah, I don't really see Valve putting out all the stops to make sure the Windows experience is the same as Steam OS, on a device that's built by Valve for Steam store. They'll likely support for some features and maybe a few drivers, but I just don't see them putting in double the effort to make both OS's 100% the same/compatible on their device, when we kinda get the hint in the room, that Valve really want this device to push their OS (which Steam machines failed at doing).
If I was Valve and was trying to push my own Linux distro to tempt users away from Windows, I'd honestly just focus on pushing my own space, instead of someone else's.
Step right up come on in, feel the buzz in your veins, I'm like an chemical electrical right into your brain and I'm the one who killed the Radio, soon you'll all see
So pay up motherfuckers you belong to "V"
