Curious if you noticed any changes post-commitment. I'm not worried about my son letting off the gas once he accepts an offer. He's self-driven like I assume most kids in his position are. But do worry a bit about the added stress of having to "live up to" being committed early and all the pressures and social dynamics that might come along with it.
My son has two club teammates who have totally dropped off after committing. One committed summer after his 8th grade year to a Top 5 program. The other committed after his freshman summer to a P5 school. When my son committed the head coach actually said, "Don't let up like_____, _____, and _____ have been rumored to do." These coaches know everything about every player. As small as you think that world is, its much, much smaller.
Every player knows on every team they play who's committed and where they are going. Your son will get used to that pressure or he wont.