I agree with your premise, but I think it is a bit more subtle. More like, "All things being equal, a woman would rather her long-term mate look like an underwear model rather than Seth Rogan." She'll accept that he is not in shape, but would prefer if he is in shape - again talking about a long-term relationship. Hookups, like Romance novels, are not the same as long-term relationships.

I also 100% believe there is a calculation in each woman's head as well: "If he looks like that, he will probably expect that I keep myself in shape as well." If you are one of the lucky guys like me who has a partner who wants to keep herself in shape for herself (and not for me) then great. Otherwise, I believe this can lead to tension/stress in the relationship. I've seen this in a LOT of my female friends over the years who are cool with their husbands getting dad bods because then there is no pressure on them to stay in shape.

I have a relatively long-term female friend who has given me wonderful confirmation bias of my theory. She's well-trained, but her long-time boyfriend looks like Santa Claus (not the Kurt Russel version, the Coca-Cola Version). She accepts that for various reasons but would prefer if he were better trained.