It could just be insincere sex talk, because he thinks that's what he's supposed to say or because he wants you to feel good about yourself. There's a thread on the forums where some people say they tell every man that he has a large cock. It could be that sort of thing, just an ego boost. It could be totally sincere!
Honestly, the only times men have specifically mentioned it was as a sort of apology for not lasting longer during intercourse before orgasm, and that's after
Although one ex-boyfriend supposedly said something extremely crude and truly offensive about what it's like to have sex with me to my new boyfriend, about the pompoir thing I do, and that was sort of about tightness. They hated each other, so I could never figure out if the new boyfriend made it up to make the ex look bad, or if the ex had actually said it in order to rattle the new bf, because either scenario seemed equally likely. They really
hated each other.