Finger dexterity has been measured by tests. There are those who have it (fast pickers, surgeons, etc.) as well as tweezer dexterity (watch makers, flat pickers etc.) There is a genetic potential for this. Strong hands and strong fingers figure into it regardless of hours of practice.

Musicality is something else again. Also, this is subjective because what is musical to someone might not be to another.

Musicianship is something else again. When these three abilities correlate, you have the fine emergence of virtuosos. Musicianship might be gained by musical training but not necessarilly. It's an ability to absorb the musical language and it's complexities. Some can do this without extensive musical training. (Charlie Parker, Django, etc.)

Practice helps up to a point. Then the genes determine what happens.

Frank