How does it help the batter in between pitches of an at-bat to be told that she should've swung at the last pitch?
If it helps, I'm all for it, but my belief is that the batter needs to be focusing on the pitcher and not relying on help from the outside, which I view as a distraction, unless it's basic encouragement, which doesn't need to be processed like a critique of each pitch does. I'd rather analyze her pitch selection after the at-bat is over. The situation changes after each pitch and with every new count. Doesn't matter what she should've done on the last pitch. It's about the next pitch.
It is about the next pitch. I think the implication is pretty obvious; "now you've seen it, if you see it again let's be swinging at it."