Why does a doctor squeeze a newborn's to get the milk out?

My 13 day old granddaughter went in for her two week check today, and my daughter said that the doctor squeezed her until he got a drop of the newborn milk. She checked with other people that had him as a pediatrician and they said that he normally does that at the two week check. Does anyone have any idea why he would need to do that? He is an excellent physician in all other regards, and it is a two month waiting period just to see him because he is so sought after as a skilled physician. I wish my daughter had asked him, but she is very shy and didn't want to. There must be some reason he did it - anyone know?