It can be beneficial in terms of performance if done right. The native Linux build of Baldur's Gate 3 runs considerably better than the Windows version via Proton, even though the Proton version already runs better than it runs on Windows natively.

Good question. It means to me that developers thought that Linux as a platform was worth targeting. One could conclude, the more Linux ports we see, then more people must be using Linux. It's my dream for us not to be treated as second class citizens where computer operating systems are concerned.

On paper, a Linux version of a game would perform slightly better, because they wouldn't have to use Windows system calls for synchronization and disk I/O.

This seems to be true for the games in my Steam library that have good Linux versions, though I can't comment on the performance of bad ones because obviously I play those through Proton.