a coach telling a pitcher to "shorten the stride" is essentially telling the pitcher to "let it go earlier". That's all shortening of the stride does, it brings the release point up quicker.
Personally, I don't think anyone has to shorten their stride to find the release point, it can be done with repetition and practice. It's just a timing issue. Shortening the stride can lead to some things which aren't so good: disruption of mechanics, tipping the pitch to the hitter, inability to regain rhythm after changing the step, etc. I'm not going to say I have NEVER told a pitcher to do this shorter stride, I have. But, it's a last resort for someone who just can't find the release point. Once we get it, I'll get her going right back to normal stride for the same pitch.
Exactly.