600yd/600m man wrote:
Javelin throw is not necessarily strongly correlated with pitching a baseball.
In Jack Nickluas' golf training video, from the beginning he urged you to swing as hard as you can and he would correct everything from that point on.
With that in mind, javelin throwers would have a step-up on an average person in "learning" how to pitch.
In my eyes, it's similar to "can a shot putter become a great offensive lineman?" Like you said, not necessarily. But with their size, speed, power, and explosiveness they would be at a much better starting point than the big guy down at the local gym.