Hey Tex. I was a swimmer in HS and then for a little in college. Did the whole club swimming thing when I was growing up, so I know how good shape you can get into from swimming. Especially if you really have someone pushing you. I also know that, overall, it is good on the joints because there is no impact. I've just heard and speculate that the repetitive overhead motion is not good on the shoulders. I know both my shoulders are bad, although I'm not sure if its from swimming or doing a lot of heavy bench pressing after I was done swimming. What you are talking about is probably good for the legs and core. We used to do a lot of them in practice as well.
I think for pitchers, sprints and other explosive leg work, like the stadiums you are talking about are good as well. Really not trying to be abrasive. I'm just thinking all that over the head rotation from swimming might just be too much for a pitcher.