During start up the N power climb to +/- 60% then reduce, so at this time parking break is very useful. But AFTER the start up, Parking break is ON because the plane will go forward. For the TAXI the pilot doesn't need to push the throttle, the plane move by himself with throttle at zero.
I'm back on the topic :p For you, during start up, the plane doesn't have to move ? I've got a friend working at Luxeuil AFB in France, he told me that one day a M-2000-5F (same start up procedure and same engine than C version) pilot forgive the parking break and his plane have moved forward by 5 or 6 meters in few seconds... I think that the problem on the Razbam plane is the bumper of the nose gear, is too flexible...