It's been my experience that this bowling motion, with the subsequent HELLO ELBOW finish, is the default GUESS as to what a pitcher should do to throw straight (i.e., throw straight strikes). As I mentioned a 1 1/2 years ago, when my DD was a freshman in high school and she had only roughly a half a year of pitching experience, the HS coach and an assistant approached her asking her if she might consider this very motion.
What they were essentially telling my DD was that I, her pitching coach, didn't know jack shxx about proper pitching mechanics, because the IR approach I was trying to instill in her mechanics were foreign to them.
When you aren't really a student of correct pitching mechanics (i.e., you don't really know), by default you think this bowling action with hello elbow is the correct pitching motion, because it's what people GUESS might be the correct motion. And, just because something looks foreign to you doesn't mean you are correct and they are incorrect.
The key is knowing that you don't know what the top pitchers in the world do. You don't just guess without investigation.
P.S. The young lady in the picture above is likely a very nice gal with very good intentions. BUT, best intentions aren't always best results.
it is hard to believe you are telling dd the best way sometimes when people with better credentials are telling her something totally different. i keep showing her the video and telling her who these people are that are also doing it wrong.
I am not a pitching expert, but I would suggest being more concerned with making sure your DD is throwing with an IR motion vs. HE than you are about "brushing". I think brushing is just a term used to describe keeping her hand next to her body during release. This helps prevent getting "off plane" during her wind up, and is also more deceptive when all pitches are released from approximately the same point.
When my DD's release point gets away from her body, primarily on her curve ball, she has a tendency to "shank" the pitch high and outside. Keeping the release next to the hip helps control the location.