The problem is, that would be going down the autonomous member selection slippery slope, same as panhellenics cannot say that women must have recs to rush at schools where you are in actual practice cut almost immediately without them. In the OP’s example...that’s entirely the sorority’s prerogative. If they want to give someone on her way to flunk out land a bid, they can.
Plus since women are coming from all different schools, the university would be opening themselves up to accusations of reverse discrimination- as we all know a 4.0 at high school A does not necessarily connote the same level of education and skill as a 4.0 at high school B.
Of course if they didn’t permit women to rush until they had an actual university GPA that might help
since everyone would be measured with the same yardstick.