I can't sit here and say you're wrong. In fact, I believe you're right. But by very little.
Babbitt actually had a better vert and was quicker in the agility drill. Johnson was faster in the sprint. And in game footage (yes, yes I know, but that's all I have of Babbitt), I think he looks damn explosive. I'm not hoping to see it either. It's just there. It's not Joe Alexander whose explosiveness was more a result of his overall strength/lifting. It's pure fast twitch fibers in my opinion.
I think you make a good point. I'm looking at old video of players like Kobe, Garnett, Amare, Shaq, etc. in high school, and you could see even back then they had 'fast-twitch' athleticism. The ability to make explosive moves, change direction quickly, finish a play with really quick, crisp moves, etc. The stars all had this ability from the start. Babbit does have some of this.
All the pro players are good athletes, but the best players can play at a whole other speed and make crisp plays. This is what separates the stars from the role players. John Wall obviously has it. So does Favors. So does Cousins too, but he's carrying too much weight (which makes me compare him to a bigger version of Charles Barkley). The question with players in our range, like George, Babbit, Henry, and Whiteside--all players who look like they could be game-changing athletes--is whether they have this explosive quickness. It's hard to tell in workouts, because it seems like everyone is basically pacing themselves and cruising. You're right that some of Babbit's footage from college looks pretty good.
It's also possible to train for speed and coordination--the high-twitch effect. For example, Dennis Rodman used to do aerobics and agility drills that enabled him to simply get to rebounds before everyone else. So this goes back to how hard a player wants to work.
Another thing to consider is the players' "ground game." I know everyone likes to focus on how well players jump and extend vertically, but a lot of the game is actually about moving low and moving in all directions on the court. Bryon Russel was not a great leaper necessarily, and neither was Karl Malone, but both players had a great ground game. They were very efficient in their movement and could cover a lot of ground very quickly. By comparison, David Benoit could jump and extend as well as any player on the Jazz, but he didn't move very well and didn't impact the game as much.
