I’ll have to see if I’ve got a copy of an NDA I signed for play testing but that’s what I would have thought. It would be provisional on your participation not on an agreement like old school EULAs. As someone else pointed out it seems to be in closed beta or some form of early access, so maybe Valve won’t care and it won’t come back on them.
Why not back up your win 7 installation and try a different Linux variant? Or even just fuck around with Linux in dual boot/vm before transitioning? I’d have to imagine that’d be preferable to either not using the internet or risking every device on the same network it’s connected to. I swear I read an article where fresh win10 installs were getting infected within minutes of connecting to the net. Let alone 7.