That interesting. I guess different people have different experiences. I've been reselling domains off and on since about 2005/2006 and I have never had a buyer have a problem with a push instead of a transfer.
I have a push-only policy. I don't believe in getting involved in transfers. The less hands in the mix, the better.
But I would consider a transfer IF the sale was over a certain amount and it meant losing a sale if I did not engage in the transfer, assuming the current registrar is reputable.
To me, it makes no sense why someone would care if it was a push or a transfer.