Great question. Thanks for asking.
Ski touring is great aerobic base training…….provided the gear is not too heavy or trail-breaking too deep to make every workout into an ME session. You’ll know this if your legs are too shot to do again today what you did tomorrow. 1-2 of these a week, even if they slip more to the ME end of the endurance scale, is fine if you have adequate easy aerobic base between.
I hope this helps,
Scott