https://bugs.winehq.org/show_bug.cgi?id=49933
--- Comment #53 from Rafał Mużyło galtgendo@o2.pl --- (In reply to comment #48)
While I'm just guessing, it far more likely that its simply the case of the way Windows does it and the way freedesktop wm-spec describe it it should be done differ.
Just like wine minimizes windows on virtual desktop switch instead of simply unmapping them.