This percentage doesn't seem quite right. I remember in boot camp a few guys were above the body fat range for their size. They were all the muscle heads that had broad chests and shoulders. All were waived along.
High schools have sports programs. Some high schools have 60-70 boys on the varsity team. Then there are the junior varsity and freshman football teams. Toss in all the other teams and you have a good percentage of the kids that would surely qualify physically for service.
Now passing the test, that is another question. I guess a few of them are early starters and already have felony convictions, so they are disqualified.
What I think hurts is a kid that is on the ball has a lot of options. I would assume enlisting would be way down on the list of things to do.