Problem with GTK-3 apps in KDE

I have the Window Behaviour action for middle-click on the title bar set to "Toggle raise and lower", but some GTK-3 apps ignore this setting for certain windows. One example is the Compose window in the Evolution groupware suite. To see what I mean, try the gtk3-demo app (from the gtk3-devel package) which also shows this behaviour under KDE but not under Gnome. poc