I can understand speakers not being able to hit reference, but that was not the original question. The question was whether or not setting the MV to 0 would be reference level. That is dependent on the AVR exclusive of the speaker or listening distance once properly calibrated. Whether or not the speakers or amps can handle it is an entirely different animal IMO. Someone please correct me if my thinking is wrong.
Sorry replying so late, just got done with Ender's Game. Here are my thoughts, assuming I am following the conversation:
Out of the box, 0 on an AVR does not mean it will provide reference level volume regardless of the rest of your equipment. I believe it is dependent on the efficiency of ones speakers and the distance from the speakers to the MLP.
When running the automatic setup procedure such as Audysey or YPAO, the microphone will adjust output level so that SPL at the MLP will be reference when the MV is set to 0. Without running this setup procedure, the AVR has no way of knowing how loud content will be at the MLP, as this is entirely dependent on ones speakers and distance to MLP. The AVR then determines how much power needs to be provided based on that .
This is my understanding, so feel free to correct me if I am mistaken.