Unreal Engine 4 fullscreen width squashed with Proton 7.0-1

Compatibility Report

• Name of the game with compatibility issues:
  • Dragon Quest XI S (1295510)
  • Octopath Traveler (921570)

System Information

• GPU: RX 6700 XT
• Driver/LLVM version: Mesa 21.3.7-1
• Kernel version: 5.16.11-zen1-2-zen (possibly also Steam Deck kernel)
• Link to full system information report as Gist: still can't copy full report because of https://github.com/ValveSoftware/steam-for-linux/issues/8124
• Proton version: 7.0-1
• Arch Linux

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

Symptoms

With Proton 6.3-8:

With Proton 7.0-1:

Same problem with DQXI S. My theory is that this regression is affecting UE4 games, to test that I'm downloading Ace Combat 7
EDIT: Ace Combat 7 works

Reproduction

1. Install these games with Proton 7.0-1 and above (including Experimental)
2. Revert Proton version to Proton 6.3-8 and see that those games work perfectly

Proton logs

steam-1295510.log
steam-921570.log

Start with the reproduction steps and compare the attached Proton logs for Proton 7.0-1 versus 6.3-8. Investigate the fullscreen behavior in Dragon Quest XI S and Octopath Traveler; done means their fullscreen width is no longer squashed under Proton 7.0-1 and later.