Plenty of threads about P+C already, especially this one
http://www.flyertalk.com/forum/hyatt...er-thread.html that contains about all you need to know about the rate.
But each hotel decides what availability to offer for P+C and when to offer it. The reply you got is a bit daft since there is no fixed quota. Although it's very easy to imagine that if there was any availability of the P+C rate that it's already been booked. People do tend to plan ahead :-).
Rates at the GH Berlin are often cheap though, so cash might be a better option anyway.