Ive finaly found my rule book to look throught and find he didnt write it in the rulebook but luckiely i remembered where i had seen it so here it is, StS is Strike to Stun the interviewer and TP is Tumas Piniren the creator.
StS: This seems to be an important question for many Mordheim players: why is the number of models in a Witch Hunter warband limited to twelve?
TP: The character of the Witch Hunter warband is a compact, very well armed and equipped group of religious knights. It is the character of warband, and their special rules and equipment reflect this.
I actually would have liked to tinker with their rules just a little bit more(to allow them summon a few more zealots before a fight and allow them to ignore rout tests caused by dogs/rabble), but I was very wary of trying to make any warnband stronger than others. I felt that Witch Hunters with no drawbacks would have been too good compared to Mercenaries.