Fingers on Top of the Ball is one of those cues that is both valuable and defensible in small doses, but can cause serious problems when taken too far.
Some related topics include...
Fingers on Top of the Ball (INTO/AT Foot Plant)
"Keep your fingers on top of the ball" is a common cue, but there are two distinctly -- and significantly -- different ways of following that cue.
Henderson Alvarez vs. Justin Verlander
Henderson Alvarez keeps his fingers on top of the ball into/at Foot Plant.
That is a problem because it creates a serious Timing problem that I call Flat Arm Syndrome.
You don't have to look any farther than Justin Verlander to see a dominant and durable pitcher who does keep his fingers on top of the ball, but only during the early parts of his delivery.
However, Justin Verlander doesn't keep his fingers on top of the ball into/at foot plant.
Instead, at Foot Plant, Justin Verlander's fingers are on the side of the ball and he is pointing the ball at third base, not pointing the ball at second base.
I'm still trying to figure out exactly what cues he uses, and why he does what he does, but Matt Harvey is a perfect example of a pitcher who keeps his fingers on top of the ball for an extended period of time.
By that I mean INTO or even AT foot plant.
Matt Harvey Frame 1
Matt Harvey Frame 2
Matt Harvey Frame 3
Matt Harvey Frame 4
In my opinion, that is part of the reason why Matt Harvey can't stay healthy.
Connor Jones is another pitcher who keeps his fingers on top of the ball into/at foot plant...
...perhaps because he was taught to make the Power T...
...and who, in my opinion, will struggle with effectiveness and injuries as a result.