Yes - I remember Cambridge had a very bad run in the 80s because of that - but then they started playing the same game and playing it somewhat better.Yes, there was a time when the Cambridge crew was mostly undergraduates and the Oxford one was mainly professionals. That was the underlying cause of the 1987 Oxford mutiny - the ringers thought they were above training with the students.
I knew of one international rower who was recruited to Oxford and on his arrival announced that he was going to give up rowing and concentrate on his studies. There was serious talk in his college of withdrawing his place on the grounds of misrepresentation, but sanity prevailed when they realised just how bad that would look.
It would be nice to think that everyone in both crews were there on academic merit but I somehow doubt if that is the case.