In the Sea King, you needed differential pedal to disengage the heading hold with the ASE in - since not many pilots sat on the deck with differential pedal pressure any heading change of the ship would cause the yaw channel to try and swing the tail. Hence the ASE disengagement on Sea Kings.
ISTR the 412 has an irritating yaw trim function but I don't think it has a yaw channel heading hold - that is a roll channel function in the upper modes of the AFCS.
Short answer is no, I don't think you need to disengage the AP on a deck unless it is moving a lot but I would go from ATT to SAS mode.