this makes sense. Plus the article notes it protects the batters by reducing wild pitches. I don't see how you can argue that it's OK for batters to use substances like pine tar to improve bat grip but it's not ok for pitchers to use it to improve ball grip. It doesn't sound like there's evidence that these substances are altering the pitches. Come up with a standard concoction and make it legal for everyone to use it.
It’s not hard to argue the difference. One only applies to the grip on the hitting implement, the other can reportedly enhance spin rates, which has been the target of MLB rules since the outlawing of the spitball.
