@GeorgeAnderson All the responses have been great but I want to add something that I think others have not touched on. I think your question has been answered but in order to further reassure him, I would say it’s always an option to go through those two training phases and just substitute VO2max workouts with threshold or supra-threshold (105%-108%) sessions.
If you look at those plans, SSB1 and SSB2, you’ll notice that with a minor exception SSB1 doesn’t have any VO2max work. So he should be good there. As for SSB2, VO2max is the Tuesday workout. Even if he substituted another type of workout he would likely make tremendous progress.
Now, before everybody jumps on me, I’m not saying a threshold or SS workout is the same thing as, for example, Taylor -2 or Bluebell. They’re not. But you’re still doing the bread and butter workouts, namely Sweet Spot, Threshold, and Over-unders. Although cookie cutter in some ways, these plans are very flexible. And I’d hate to see someone put off just because of one, arguably less important, type of workout.