That is not true. Especially after you leave the 20s. Men in western nations have a loneliness problem that women never experience as a group to that extent. After women give up on the prospects of children which usually happens somewhere in the 30s, the dynamics of sex and relationships changes dramatically with men by far being the more clingy ones.

Hmmm....men are fairly highly pressured by (modern western) society to not get attached after sex, and are somewhat likely to deny or at least play down feelings of attachment that they might naturally feel - even to themselves.

I'm not sure how you'd be able to control for that sort of bias in any kind of rigorous study, or how much variation might be left if you did.