Ok, i understand that a reincarnated baby wouldn't want to drink his mother's milk because of his adult mind/soul and apprehensiveness towards it.
But other people seeing it as a sign of "gentlemen", is really odd. I mean, any sane person would actually be worried if a baby doesn't drink his mother's milk, because they are needed for growth, development and immunities (i guess that's the reason why MC ended up having a girly body, even though he is a boy).