1.25V is after the preamp, and thats the maximum output. Bear in mind that because of the preamp, it adds gain and eq, less the preamp, the 81 probably only has about half the output of the z2n.
Another reason why it would have such a high voltage spike would be its focused eq, where EMG can tune each pickup to blast out a certain frequency. 2200Hz for the 81 if im not mistaken.