Too bad he didn't really address why people regularly do multiple exercises for a given muscle group to begin with. For example, I think many experienced lifters do multiple exercises because each exercise (if done intensely) makes them feel sore a day or two later in a unique area. But he is making it out to be that if you just regular bench presses intensely enough you'll hit all the parts of the chest, but I'm not so sure about that. So for example, I noticed that my upper chest just wasn't developing at the same rate as my lower chest, so I completely abandoned doing regular and declined bench presses and these days I only do inclines. And I can tell that method works because I feel sore in my upper chest a couple of days later in a way that I never feel with the regular and decline presses, and also because I can see my upper chest filling out over time.
Thought I'd throw in this video as well: The guy's a bit pedantic, but I agree with him. Also, I like to see him critique Brad Schoenfeld, whose (fairly discredited) research has been polluting the Internet with volume training.
I understand your point. If you read the comments section on YT where he responds to questions, you'll see that he's not dogmatic about it. He refers to it as a general concept rather than a hard and fast rule. But even in his originally-proposed ultra-minimalist routine (the "Big 5" in BBS), he hits the back at 2 major angles and arguably the chest, because shoulder presses do work the pecs somewhat at a significantly different angle. Perhaps I'm misinterpreting, but I think he was probably referring to more nuanced angles as being unnecessary . Some gym goers do several different exercises for a single muscle group. I think that's overkill. For my rudimentary purposes, I don't have time for nuanced angles. So for back I would do pullups and rows, while for chest I would do dips and slow, full-range pushups with feet elevated and arms not quite locking out at the top of the movement. And since I do pike presses in a similar fashion for shoulders, there's a bit of chest work in there as well, along with a number of other muscles. So I essentially agree with McGuff.
Well, I don't think HIT necessarily means a single set per major muscle group. And if you do more than one, then it is probably better to do a fairly different exercise rather than a meaninglessly different one or multiple sets of the same movement. Also, a significantly different movement for a major muscle group will address different stabilizer muscles and so on. Okay, yeah, at this point I'm talking through my hat. But you knew what I meant.
This is the 40+ year old Mike Mentzer debate. Mike Mentzer would do one set per body part and say everyone else is wasting their time. Of course though, he was 70s geared up and a champion body builder with amazing genes. His brother was a beast too. You also couldn't sell magazines with routines of doing a set of squats and call it a day. That is all really too simplistic though. If you do 30 seconds of work and then take a minute and a half rest there is a huge conditioning and cardio aspect if you are doing that for 30+ minutes. If you are doing multiple movements and sets per part you are surely burning way more calories. The optimal conditions are not going to be 1 set per body part and then lay on the couch all day so you don't burn calories instead of just eating more. I have a picture of myself at 21 though that was the widest and most developed my shoulders and chest ever were. I was sick of lifting at that point and would do a drop set of side lateral raises and a few sets of incline dumbbell press once a week. Other than that I was doing sprints 3 times a week on roller blades. My secret was nothing other than being 21 and having good genetics for building muscle. In late 40s without TRT yet that doesn't work at all for me now. 1 set a week, I wouldn't even look like I lifted.
I think the idea is one set per exercise, not necessarily one set per muscle group. And with a focus on compound movements rather than isolation. It doesn’t have to be only once a week. Whereas I was doing twice a week not long ago, I’m presently at a frequency of 3x/2wks. What do your workouts look like now?