The sooner the better..... observed a pitching clinic last weekend where some guys I highly respect and who taught me a lot about coaching 10-12 years ago were still teaching pitching like they did 12 years ago. I was cringing as they were coaching some natural IR out of 7yo and 8yos.
My last two days up one of the places I teach, there were two different girls in the cage next to me who looked like they had some great athletic ability. But their mechanics were terrible. I'm positive at least one of them was taught those mechanics by an outside instructor (not bucket dad or mom), probably both. Made me sad to think of what they could do if they used their bodies efficiently.
Went to a Big Al Baseball coaching clinic last night. He spent ~15 minutes at the beginning quickly covering softball pitching. Was quasi-HE, but interestingly at the end he showed two backward chaining IR like, almost brush triggering drills. He gets his FP information from Michelle Smith. Said something to the effect she is changing some of what she is teaching and demonstrated it. Sounds like she is at least aware of IR/BI and is changing slightly in that direction.
Kind of what I've seen in overhand throwing instruction the past 3 years or so. They are still using some of the old school cues, but describing it closer to a HLT than they used to.