Maybe we should clarify here what Advanced MCACC does. It corrects the delay, power and phase for each speaker across the full spectrum in order to make any home room as closer as possible to a THX certified environment. It tests 9 frequencies between 63Hz and 16KHz for all the channels. low frequencies below the crossover are equalized as well. Advanced MCACC does a deeper analysis than Audissey XT.
Another different subject is the fact that Pioneer is following the Dolby Labs recommendation of having a single crossover frequency since under 80-100HZ is impossible to hear the source of the soundwave because the wavelenght is several meters long and we can not detect the phase shift between both ears. Having several bass sources is useless unless you have them all in sync with the same spectrum, this is a single signal. A single bass source is better in order to maintain a controlled soundfield in the whole listening environment while requiring less power requirement. This is why THX has a single LFE channel with clear specifications in this direction.