To be fair, it's not a loophole if an exception is spelled out in the rules. And regarding your theoretical in your next to last paragraph, that isn't theoretical. The exception address this and spells it out: parade prep doesn't count against your 10 hours. Maybe not spelled out the way you would spelled it, but it is spelled out.

And, yes, there are bona fide loopholes in the CCR, but this isn't one of them. No ambiguity here.

I was once told by the UIL Music office that, "If there isn't a rule forbidding an action in the CCR, then taking that course of action is not illegal."