The answer, as with most things, is: it depends.
Improving maximal strength in the bench press might have some carry-over to throwing a baseball but that carry-over is pretty low, if not negligible when viewed in the context of an entire training program. That being said, increasing strength and size of the prime movers involved in pressing will likely make specific training methods (exercises that mimic the speed and muscle actions involved in throwing) more effective. Also, bar speed matters. Training with faster bar speeds likely has a better carry-over to throwing than training with slower bar speeds all the time.
It’s all about when and how you incorporate these exercises into an individual baseball player’s strength and conditioning program. Importantly, maximal strength gets less and less important the stronger you get.
Unless it eats up training volume that could be otherwise dedicated to more specific – and, thus, effective – training methods. I’m not against getting bigger or stronger, particularly for younger athletes. It just has to fit in with the bigger picture.