What a load of hooey. I only get gains anymore (I've been training 15 years) When I go beyond the status quo, which usually means going beyond failure. Just increasing weight a bit here and there and/or doing an extra rep or two doesn't provide enough of a shock to force adaptation- ie increased muscle size.
I don't agree that you have to train "explosively" -we aren't bombs, we are humans. That is possibly applicable to powerlifting and more so O lifting, but for building size, you can build it more safely by moving in a controlled manner. Can't build strength this way? Ridiculous- I have worked up to Squats with 515 for reps (615 for 4 half Squats) close grip pulldowns with 360 for reps, 315 smith machine inclines, 225 overheads, Hammer leg extensions with 470 for a few reps, etc. That's fairly strong, I would say.
Having said that, some people who don't tolerate high intensity stress as well - ie., those with poorer recovery ability, might benefit from doing say 3 subfailure sets as opposed to 1 or 2 to failure or post failure sets.