[Window 7 + TCC latest 64-bit] "GATWDA Default" is the title of my Firefox 31 (with the default page loaded) as determined by echo %@WINTITLE[<ff_pid>]. activate "GATWDA Default" hide does nothing, while activate "GATWDA Default" tray puts the Firefox in the tray but doesn't hide it, and activate "GATWDA Default" show will untray the - not hidden - Firefox... (the behavior seems to differ slightly from my other computer).
The behavior doesn't seem to be bound to Firefox; it also happens e.g. with VLC. It does not however happen with e.g. Explorer windows.