It’s like Overwatch, Dota 2, and Team Fortress 2 all baked into a pie.
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.
At best they ignore it. At worst, they never invite the user to test anything again. I doubt they’d issue an account ban for that. Not even sure if they can straight up ban you from the platform anyway and lock you out of your games entirely; pretty sure the bans are limited to VAC secured servers for online play and the array of community features like posting on the forums.