I fully understand why this new opportunity would make your son question whether he can renege on his ED commitment.
However, this isn’t much different from the hypothetical kid who gets a surprise full-ride scholarship offer from another school, and suddenly full-paying for their ED school doesn’t look so great, even though they can afford it and understood that they were committing to do so. And that is not considered an acceptable reason to break an ED agreement. (Whereas, an unacceptable financial aid offer would be an acceptable reason, or some sort of family tragedy that completely alters the student’s ability to attend the ED school.)
One possible way out of this impasse: Is it possible that the recruiting coach would be willing to guarantee a roster spot if your son took a gap year and matriculated the following year? I’m not exactly sure how the rules would apply to such a situation, but I think that if the student did not matriculate anywhere in the year they were admitted for, then breaking the ED commitment could be more acceptable, and he’d have a clean slate for the new admissions cycle. (And maybe he could also train during that year and avoid the benchwarmer problem that others have mentioned…) Maybe this wouldn’t work for you, but just a thought.