Nobody has really tried to systematically replace "traditional" reps the way IART is doing with zone training.
People have definitely flirted with this idea, from 21's to stage reps, but nobody has systematically applied it to training in general.
So, like or hate IART, I am forced to concede that it's actually a pretty interesting idea.
Put differently, try it. I did a single set of bulgarian split squats in jreps style, moving rythmically with brief pauses, doing 12 half reps in the bottom, then the top half, then full. Not to sound like Vince Basile, but my ass was so sore the next day that I could barely walk, and it is REALLY rare for me to get a sore ass from training.
So, I think there is something to it. Just my $.02.