Flash in particular doesn't think it should be in FS mode if it doesn't have
the focus.
It is. Most importantly, there's a race condition: if the flash
window doesn't get the focus fast enough, when it goes into FS
mode, it will close. But this "trying to outsmart the WM" also
means you can't open the scratchpad while flash is FS, can't
switch back to another WS while flash is FS, or the window will
un-FS.
So this is generally a flash problem with focus, very interesting,
thanks for the insight.
Obviously letting anything actually have focus control is uncool so
that's a problem.