Yes, you can force it on all games if you want. I'm currently playing many games on the latest version of Proton.
It might be named a bit confusingly though, I'm at work and don't remember exactly but it might be worded something like "Override proton version for all games" which also enables it for games not explicitly marked as compatible.
It might be named a bit confusingly though, I'm at work and don't remember exactly but it might be worded something like "Override proton version for all games" which also enables it for games not explicitly marked as compatible.