WFM LM21 Cinnamon
Sorry, Works For Me using Linux Mint 21 Cinnamon
I'm running GNOME 42.9 and Wayland windowing system.
My post illustrates that the behaviour is dependent on the window manager/Wayland compositor, it is not under the control of Geany shown by the fact it works on my setup which is different to yours. There have been no other complaints (that I recall) so its likely it works on most systems where it could reasonably be expected to (for example tiling window managers do not allow windows to place themselves, the window manager packs the windows as tiles, so positioning requests are not expected to work with one of those).
I'm not sure that any other contributors use your setup, and as far as I can recall nobody has complained, but if they do they may be able to confirm the problem and then can investigate if the problem is GTK, Gnome or other and if/how it can be fixed, or you may be able to do so yourself, perhaps there are Gnome settings that may influence it.
I tried both GDM and Xorg display managers and it's the same behavior.
IIUC the display manager is what runs before login and before the windowing system runs, so its not relevant to the Window manager that runs in your session. Or do you mean that you select a Wayland or an Xorg session? Note that an Xorg session is different to running a Wayland session and using XWayland.