Ive read 2 or 3 studies over the past couple years that came to the conclusion that fast explosive reps were better for developing power but slower reps in the range of 2-3 seconds up and 2-3 seconds down worked better for muscle hypertrophy.
My guy has me do very controlled reps. Up and down with a very focused contraction with each rep. It's grueling. Has me hit failure at rep 7-8 then forces me to go to around 12. Hate it. I mean I love it. Lol.
The problem with HIT training is that people become "HIT Zealots" after reading his book, and think that is the ONLY WAY anyone should train, ever. Basically they become brainwashed by Menzer's superior logic.
Unfortunately, that's an easy enough trap to step into, particularly if you've managed to make some decent gains, at least initially, using a Mentzer-style approach to training. I know I was pretty convinced that I'd found the holy grail there for a while anyway. Mentzer's writings definitely reinforce that attitude and if you then start reading a bunch of Ayn Rand on top of that, like I did, it's hard not to end up sounding like a pompous ass before you even realize it.