Cartridge output question

My main cartridge is an AT PC-1 Supreme which is currently on it's way back to Japan for evaluation. I have a Denon 103r that I use when my main cartridges are not available.
Even though the 103r states an output of 0.25mV compared with the PC-1S 0.4mV, I find the Denon has far more gain (at least 12dB) than the PC-1S in my system.By this I mean my stepped attenuator needs 12dB less attenuation to deliver the same volume from my speakers for the PC-1S

Could this just be a case of the output being defined at different frequencies and velocities between manufacturers. I would expect small differences but nothing of this magnitude.
Well you did say the Supreme is going back for evaluation?
I find outputs seem to vary a bit. I also feel that the better your cart (and cart-arm synergy, setup etc.) with subsequent benefits to lower distortion, better tracking etc. the quieter the perceived level....ymmv
May be a loading issue or a defective Air Tight which would be unusual but you did have to send it back.