I wouldn’t say “out of line,” that’s harsh phrasing.
But any coach, manager, PT, equipment person, etc. will not discuss a health or medical issue of anyone’s without that person’s direct consent.
Sometimes those protections seem awkward and over broad (“this isn’t about her medical issues, it’s only about a knee brace—this is generic advice for anyone using a brace”), but anyone associated with the team should not talk about anything related to someone’s health.
If I had to guess, the coach knows you mean well, but they are letting it lie and not even acknowledging the health issue of the player by responding to this in any way with you (or anyone else!).
In other words, it’s not personal, just don’t mention it again 