Taking the admissions question off the table for a month moment, the question of how a student nurtures a talent outside of BS is a big old “it depends.”
Some schools are more flexible than others. Some schools will insist that the student’s primary focus is the BS, and will not allow outside activities to be used in lieu of the schools required activities. Other schools are more flexible.
However, even where the school is flexible, the logistics of scheduling, transportation, etc is complicated and will require a great deal of commitment from the parents.
As far as admissions, a hook is something that a school needs, or at least strongly wants. A school wants legacy for potential future donations. A school needs athletes for its teams. Does a school need a boxer? Probably not. It may help in admissions, but it’s probably not a hook.