I’ve done their ultra running plans for mountain running. The volume was too high for me. So I just scaled to the duration of my event. Instead of back to back 4 hour runs, a one hour run one day and 3 the next. That sort of thing. Worked great. I maxed at 12 hrs/week for a few weeks, but most were right around 8 hours. Ran 40 miles with 11,000 of vertical and wasn’t sore the next day.
I think the thrust of it is: here’s an ideal program with a proposed set of concepts and workouts. My guess is, if you scale that to meet your training availability, it’ll work really well.
Specifically, I’d guess 5 hrs of zone 2 a week, if maintained as a base for several months, and the ME and strength on top, is going to be great. And if you can do, say, 4 weeks of bumping that to 8 hrs and scale back the strength work to maintenance levels for the 4 weeks, even better.
Substituting high intensity for zone 2 is qualitatively different because it works a different energy system.
Anyway, for what it’s worth, I think folks on the thread are right on. Don’t let the perfect be the enemy of the good - any program with consistent zone 2 aerobic work, strength work, and an ME component will be awesome if you stick with it and progress/periodize in a reasonable way.