It's not just about 70%. It is also about the number of matches at your weight. The NCAA rules don't account for switching weights or for injury. They may even have left this loophole open for a reason.
I don't believe in tax evasion, but I do encourage tax avoidance. That is to pay what you should, and avoid what you can by legally taking advantage of any rules within the tax code that allow you to reduce your taxes.
By the same token, if the loophole exists in NCAA wrestling, a coach would be a fool not to take advantage of it. I would rather see a coach that is proactively giving his wrestler the best opportunity (and that is what this is, just an opportunity) to earn a spot into the NCAA tournament without leaving it up to the NCAA selection body.