I can confirm this behavior on my machine. And after a (far too) long internet search, I think it might be connected to this Muffin bug report from 2023.

I checked every single setting window and tab and scoured the gsettings with dconf editor and as far as I can tell, there is no way to disable this strange window snapping behavior when dragging a window with SHIFT held down.

Of course, the fact that people keep confusing snapping with tiling did not help in my search.

Holy shit! Where did that one come from? I’ve been wanting to replay Ambermoon again for quite a while now. Thought I had to go through WinUAE for it. And now you post this? Thank you so much for posting this!