Yep... well, it performs the "minimize all" function which I discribed in my post. So, indeed, windows which don't have a "minimize"-function in their systemmenu wont be minimized, and this indeed includes programs such as rainlendar, kapsules, etc...
It is indeed a "solution" for the problem. Nice tip...
For people who don't know what we're talking about:
CookieRevised's reply to Messenger Plus! 3.20