i don't believe he is uncomfortable with sex. rather he has lived for such a very long time and thus is unphased by it. similar to how there's this presumptuous notion that older people would be mind blown by sexual topics when in actuality they've seen all that and more.
sure, part of the stereotyping may be due to older people being more inclined to be devoted to christianity but asterion would be even further away from that given greek mythology is all sorts of kinky