https://bugs.winehq.org/show_bug.cgi?id=46502
--- Comment #6 from Reinhold reinhold.hoffmann@hotmail.com --- Again, thank you very much for your immediate response.
Quite frankly I am not an expert what Wine does and what a windows manager does and what the load sharing between both instances is.
Your response basically says that the behaviour of the message flow for these two messages is different for different windows managers. E.g. Gnome for Ubuntu (now in Ubuntu 18.04) behaves differently than the "Windows" window manager (not sure if this is the correct word for un-opting "allow the window manager to decorate windows") or other windows managers e.g. KDE or e.g. Winebottler's window manager on a Mac (works nicely here). This different behaviour impacts up to the app. This means that a Microsoft Windows app needs to deal with the behaviour of the different windows managers unless the option "allow the window manager to decorate windows" is unset.
This is new to me but I am still learning :-).