This issue is also present in the Utawarerumono Series, which is made by the same developer, Aquaplus. Switching to Proton 8.0-3 fixes the issue in these titles as well. I'm putting this here since it's the same issue but if it is better to open separate issues for each title let me know and I can do that. I have an RX 6950XT.
Utawarerumono: Prelude to the Fallen (1151450):
steam-1151450.log
Utawarerumono: Mask of Deception (1149550):
steam-1149550.log
Utawarerumono: Mask of Truth (1151440):
steam-1151440.log
Game now runs with the latest proton experimental bleeding-edge.
proton experimentalx2 2023-08proton 8.0-3x2 2023-08
Compatibility Report
System Information
I am unable to provide runtime diagnostics as it still crashes GPU driver.
I confirm:
steam-2432110.log
Symptoms
Attempting to start this game using Proton Experimental (or bleeding-edge) causes the game to crash on startup with this message:

Does not crash with Proton 8.0-3.
Reproduction
Start the game with Proton Experimental (or Bleeding Edge)