Another thing that wasn’t mentioned in the video that Proton does is it also – sometimes, depending on the game – checks a list of known requirements for a game and installs them through winetricks, or makes other recommended changes to game files that are known to make the game work.
When Proton is updated and the patch notes mention that a game was fixed, it’s something to do with this part of the process. A certain library, or whatever was missing and Proton installs it for you behind the scenes.
It also runs WINE through Steam’s launcher (aka Steam Linux Runtime) which has some common redistributables (aka Steamworks SDK Redist) built right into it, and it also runs appropriate anti-cheat solutions (aka Proton EasyAntiCheat Runtime or Proton BattlEye Runtime).
It matches for non-primes and doesn’t match for primes.