I don’t think that counts as previously healthy.
Actually, it does. At least in 25% of the cases of hypertrophic cardiomyopathy the first and only symptom is sudden death. That’s not what the kid in this article suffered but it is the most common cause of sudden cardiac death in men under thirty.
If you want to watch a ESPN 30 for 30 on it in the case of Hank Gathers when he died on the court playing for Loyola of Marymount, go here: https://www.youtube.com/watch?v=EwGYQkFm9gk