Good questions. David Roeske did a lot of base aerobic runs between those killer ME workouts. A few things to keep in mind:
Runners don’t call their easy runs ‘workouts’ they only call hard workouts ‘workouts’.
David had, and has, a very high aerobic base fitness. When he started working with us he had recently run a 2:30 marathon. So his aerobic base only needed maintenance which allowed us to focus more on the higher intensity ME workouts. Most climbers won’t have such a well established aerobic base. David could stand to sacrifice some of his base as he built more ME.
As for doing upper and low body ME: You can definitely do these on the same day. I presume your upper body ME will be some sort of climbing. This will be a very high energy day so eat well before and after.