ND did this when I was there. My beef was mostly the comment that it was a matter of "integrity."
Seems like simple policy. ND had a 5 year dual degree engineering and arts & letters major program when I was there...at least, I knew someone who was doing that. I also knew someone who had trouble graduating, and he stayed beyond 4 years to try to finish up. I don't think either case was a breach of integrity, as conor suggests. And, if we allow non-athletes to do it, seems like we should allow athletes to do it as well...and again, that would not seem like a breach of integrity.
But, as you point out, these two approaches may not apply in this particular case.
Evil preaches tolerance until it is dominant, then it tries to silence good.