We can acknowledge that you meant well. A coach who is friendly is not inviting input on training, strategy, roster, etc., so while they may welcome conversation, the topics may not all be available! It wasn’t your kid, so it was pretty much off-limits.
Pretty much because if you were an orthopedic surgeon or even physical therapist who had professional experience with braces, the response may possibly have been considered, if not acknowledged. As a well-meaning tinkerer, maybe even a brilliant one, your help was less credible.
I agree with the others that if you let it lie, there is likely no harm done.