No, proton compatibility isn't really signified by the flag as it's not official support. That being said it seems Valve doesn't do much to help promote Proton

No, proton compatibility isn't really signified by the flag as it's not official support. That being said it seems Valve doesn't do much to help promote Proton compatibility either, as the only good resource I know to check compatibility is protondb.com (which you should take a look at by the way).