I think the powered out is just for basic monitoring onstage while front of house gets the stereo signal in all its glory.
For the last few gigs before lockdown, I was using the Stage live. Even for me, my monitor in front of me with my guitar in it is just mono (always has been. Even in my Bradshaw rig days) even though front of house is always getting stereo.
I can see why they did it the way it currently is but it also would have been nice to have stereo powered outs too.
It’s a great unit.