Reason - a matrix has access to sub groups as well as channels and auxiliaries. When working on theatrical shows using multiple radio mics the QMix operator can have a post fader feed of those microphones when they are mixed via a subgroup. Giving the monitor/headphone only active/required live microphones.
I’ve got around this on a show with the orchestra on headphones by giving them an auxiliary to mix themselves via QMix then using a matrix to add live microphones along with the auxiliary. Unfortunately this uses up double the flexmixes - 10 auxiliaries and 10 matrix’s.
