Quick suggestion here?
Install or update WSL as-is from Patch My PC on a test device, then run the wsl --set-default-version 2 command from within PsExec launched in the SYSTEM context. See if it does configure WSL to version 2.
I don't have a lot of experience with WSL, but I'm wondering if WSL's version is configured per-device or per-user? If the latter, and the wsl --set-default-version... command does nothing under PsExec, that may explain why adding it as a post-install/post-update script has no effect.
Install or update WSL as-is from Patch My PC on a test device, then run the wsl --set-default-version 2 command from within PsExec launched in the SYSTEM context. See if it does configure WSL to version 2.
I don't have a lot of experience with WSL, but I'm wondering if WSL's version is configured per-device or per-user? If the latter, and the wsl --set-default-version... command does nothing under PsExec, that may explain why adding it as a post-install/post-update script has no effect.