I think things start get muddled when we try to sort out
why things happen. You can make the empirical statement that your performance improved, but what factors played into that? Metabolic adaptations, psychological adaptation, improved neurological efficiency (i.e. skill), and more could have played into it, but how do you sort out how much to attribute to each thing? Maybe you made metabolic improvements, and as your movement patterns cleaned up you used less energy. Maybe as you got used to training, you were less aroused by it, and the decreased stress hormones allowed your body to remain more aerobic. We can try to parse things out by looking at how well the improvements made in the dojo translate to other areas of life, but even then it's still pretty hard to pin down.
Ultimately, we know that most training works. I think the issue when comparing HIIT with HIT with HIRT (say that five times fast) is trying to figure out when each one is the most appropriate/efficient use of time. With respect to hypertrophy, I suppose it's a question of "My goals are hypertrophy and...[what?]" If my goal is big muscles that function aerobically, HIRT might be the ticket. If it's big muscles with a high lactate threshold, then maybe HIIT. If it's just big muscles and who cares about the rest, HIT seems to do alright.
All we have to do to really figure it out is take a few groups of identical people, and put them through slightly different training programs for a decade or so, and see what the results are