FYI, vertical jump more or less cannot be trained. It is almost entirely genetic. Either you can jump high or you can't.
Also, I think many people underestimate how useful strength is in most aspects of life. From picking up groceries, to home improvement projects, to wrangling kids, to getting yourself up off the toilet (a serious problem for older people). Strength makes all of these easier.
How is this possibly true? I've increased my vertical jump by nearly two entire feet through years of training in volleyball. Everyone can increase their vertical just like they can increase their squat. It's a full body compound movement.
I think he is referring to method NBA teams select newcomers. They take well trained young person and they have them do vertical jump. Because they are well trained, their vertical jump will not improve much because there is genetic component to it. But if you are average then of course it will improve with time as you do training, for example if you lose weight you can jump higher or if you practice and improve nerve-muscle connection that will increase your power output it will also improve your jump. But at the end of the day there is genetic limit for the most part, but just like with everything there are probably exceptions...
Kinda like IQ test, if you train specifically for it, you can get better. Vertical jump is a good measure of power, same as a IQ test is a good test of intelligence.
The great advantage of volleyball is that it actually teaches how to jump.
I played volleyball recreationally for years and the jumping with arm swing became muscle memory. Last week I was teaching my 10 yo son some volleyball basics and I realized how a few extra movements can impove one's jump (specifically the singing and its timing).
Actually, most people can jump higher, because they don't know how to jump properly. Most people don't know how to stretch properly, or how to engage momentum properly, or how to break past basic mental blocks in movement. Training can teach anyone that. You can go past that and also train precision jumping, or skills that build on jumping like wall-running, or something more simple like jump-rope skills, or something difficult like flips.
In addition to the skill of jumping, jumping with weight will gain muscle and endurance. It also improves the fast neurologic response that is required for the complex series of movements when changing direction. It also trains specific muscle fibers in ways that aren't in strength training.
Much like squatting, all you have to do to start is to jump a lot. Trainers can point out how to optimize your jump. But a lot of the potential to get high air, land on top of something, or reach something high, is mental.
As he points out, if vertical jump was really trainable, every basketball player in the NBA would have a 48" vertical. But, I assure you, they do not. Only genetic freaks have 48" verticals.
The fact that everyone's vertical jump doesn't reach some arbitrary height in no way disproves that you can train someone to jump higher. All it proves is not everyone jumps to the same height. This is obvious.
Also, I think many people underestimate how useful strength is in most aspects of life. From picking up groceries, to home improvement projects, to wrangling kids, to getting yourself up off the toilet (a serious problem for older people). Strength makes all of these easier.