Who specifically are you talking about? Obviously for some players, an uptick in velocity is fleeting but it does happen to many HS kids who do maintain the velocity. It's a natural aspect of a teenager growing and maturing. The other concern is players who are a bit older who have an uptick in velocity and then blow out their arm almost immediately (Rob Whitenack comes to mind). Perhaps he was referring to Hayden Simpson, 1st guy that jumped to mind when I read his quote. Simpson and Stinnett were the ones I was mostly thinking of.