Hard to really say. I've tried to figure it out myself. There's been an uptick in the caliber of coaching and lessons that are available in the area and exposure to strength and conditioning work. A lot of the same guys leading the same HS programs and programs like Webb that have better coaches than they had previously.
I grew up playing with Daniel Norris and he was throwing low 90s before he ever got exposed to legit coaching with an East Cobb program and eventually got up to 96-97 with them. I think we had 6 kids on our 14U team, including him, throwing 85+ and no one running that program or any coach we had before that did anything special. We just showed up to our first tournament the 13U season and he went from throwing probably 70 as a 12 year old to 80+ at 13.
You didn't see anyone working with legit pitching coaches in Northeast TN but I can still think of double digit kids throwing 90+ in that Big 8 conference in the Johnson City, Kingsport, Bristol area from 2011-2013 and many still playing in the bigs or made it not that long ago. In Knoxville there were guys working with Larry Simcox and Rod Delmonico and the guys at that facility. That was about it and they're still around but they aren't pumping out the same caliber of prospects that they were when their kids were there and what ended up coming out of that dominant Farragut program.