I totally agree. There’s a ton of debate on this topic, and I never really understood why. To me it always seemed to make sense that to get your center of gravity moving powerfully towards home plate requires some amount of pushing off with your back leg, even if that’s not the focus. Even a pitcher like Nolan Ryan, considered to be tall and fall guy, pushed off with his back leg in his stride or he wouldn’t have had such a long stride. Gravity alone just can’t do that.
I think people look at hard throwers in slow-mo and see that the back foot has already pulled off the rubber at pitch release and think, “see, how could he be pushing off if his foot isn’t even on the rubber anymore.” But that way of looking at it misses the point. The pushing against the ground/rubber happens In the stride as the pitcher moves down the mound riding a strong back leg, not at the actual moment of pitch release. If you looks at the hardest throwers, most of them actually drive out so powerfully that their back foot isn’t even on the rubber anymore by front foot plant, but that’s partly because they were pushing off in their stride, not the other way around.
I agree though, teaching guys to consciously “push off” isn’t always the most effective way to get them moving the right way. So I think Roger gives some sound advice. Along the same lines, I like to teach getting the weight inside the back foot in the leg lift to help build momentum towards home plate to begin moving aggressively down the mound.
Personal note: I was always taught the tall and fall approach growing up. As a result, I had a relatively short stride and ended up being pretty upper-half dominant. I did okay with this because I was a big strong kid with long limbs and good arm action. Once I got to college and they got me working out (lifting, sprinting, med ball work & plyo’s) I saw a big jump from 84-87 mph to a consistent 89-91 topping at 94. Gaining strength and learning to move more explosively with my legs directly translated to more velocity on the mound.