Something I wonder is if this new version is a linux build specifically targeting the deck hardware+OS setup, have Larian now committed themselves to following whatever Valve does in future for changes to that setup. In any case, they've got a fallback which is the windows version on proton, but it's inverting how Valve has trained many to behave which is to make just a windows version and delegate linux support to them.

There's also been persistent speculation about whether Valve would take on the burden of releasing SteamOS as a general distribution anyone can install on their own hardware (which I think is unlikely), which could in turn affect how Larian has to treat this port even if that is just communicating what it is and isn't.