This is similar to what I read many years ago. It was about training for 100 mile events when one does not have the saddle time. It was similar. The "guinea pig" trained on shortened training session less than 5 hours a week I think it was, for about 5 month or so... Forgive me but it was such long ago. But I do recall that the strategy worked.

I like this training idea. One gripe is about max heart rate at 220-your age rule of thumb. I would be only 15yo by that rule. I'm not sure I want to be back at that age.