https://bugs.winehq.org/show_bug.cgi?id=50981
--- Comment #12 from Lemonzest lemonzest@gmail.com --- I think I figured it out, it's the window manager not doing what it's told, so I tried the following the other day, but had forgotten to update the bug.
openbox: Works blackbox: Works Mutter: (GNOME 40) Works pekwm: Works Metacity: (Gnome-Flashback) Failed Muffin: (Cinnamon) Failed
The latter two DM were the ones I was using.
The window managers that work can open the correct window sizes that are asked for in the virtual desktop settings in winecfg, so a 2560x1440 window on a 3840x2160 screen, the ones that fail do not open the correct size, they open a 1920x1080 window and crop everything else. This is probably not noticed much as most people with 4K screens have some kind of scaling applied and not a raw 100% screen like myself.
I hope this helps