I have noticed at least for me something inside the command line arg overrides seems to be causing the problem when applying resolution settings.
Given that I am testing this without setting any command line arg overrides and even after a fresh restart of UE5 the issue persists I am under the assumption that some command line argument that’s a default is causing fullscreen to break when applying resolution settings.
I don’t know which one it is as there are a ton of command line argument overrides so I’m just going to have to start trying to override a bunch of them and hope I get lucky until fullscreen starts working with it ticked. I would have hoped that “Check of command line overrides” would be no op if no command line args have been enter by myself but that doesn’t seem to be the case, it does have an effect and it does break fullscreen just by default.