This is indeed the Wayland client-side decorations as provided by libdecor:
There is work to introduce a GTK plugin to make the decorations more like the rest of GNOME…
… but this is technically out of our hands, we just provide the window surface to libdecor and it handles the rest. That said though, I’m surprised it’s using Wayland by default; as far as I know the only two environments that are supposed to do this are RHEL9 (or just CentOS 9 right now, technically) and certain Flatpaks. Is this the default SDL2 package from Fedora’s repositories? If so this is a downstream patch, and Neal Gompa would be the person to talk to about that: