If you WINEPREFIX=/home/USERNAME/.steam/steam/steamapps/compatdata/APPID/pfx/ winecfg and enable virtual desktop it fixes the no mouse grab glitch. I thought it would because it does on regular wine
It may also be useful to use the MouseWarpOverride registry key. That can help sometimes too.
This issue isn't targeted around a single game. I'm sure it effects multiple games. It's that classic wine glitch that's now on proton where a fullscreen application doesn't actually capture the mouse so when you move the mouse a tiny bit nomatter the sensitivity you spin around like 8 times.