Mentzer always used philosophy as a validation for his training methods.
It made his really foundation-lacking training theories seem more profound and well sought.
From my experience I found HIT was just a simplification of the glorified BB mags routines. And a good catch, because people following the "Champions" routines will do 20 sets to failure for each bodypart twice a week, with forced reps, supersets, etc. So when people are showed HIT they get hooked, little time at the gym and more results...not because they are getting better, just because they have cut 20 times what they were doing so their bodies are somewhat returning to a normal state...
(i say this based on the fact that most people that i know that tried HIT did it after getting frustrated with Muscle mags routines...)
To be fair some people like Poliquin had said it works, but just for three weeks or so. But I found that even if training to absolute failure can give some results ( too litle for me...)the fried CNS and adrenal exhaustion that creates affects my everyday life too much to consider it a training option.