https://bugs.winehq.org/show_bug.cgi?id=53114
--- Comment #6 from Rafał Mużyło galtgendo@o2.pl --- AFAIK, wine doesn't have a pure wayland backend and (as you've mentioned yourself) KWin - so a XWayland case, meaning still winex11.drv.
Anyway, my initial guess would go along you providing WINEDEBUG="win,event,x11drv" output (likely someone else could suggest a better selection of channels, but these seem a good start).