I think that most (straight) men will say this to avoid pissing women off but in fact, women have to reach a certain level of attractiveness before they can be considered as a potential girlfriend. So the inner beauty is a pleasant bonus while the outer beauty is a prerequisite.
I've met women who thought that a guy was not that good-looking, but eventually got together with the guy because they loved his personality (and vice versa, thinking that a guy is hot but eventually finding him unattractive because of his personality).
However, I've never heard a man say "I thought she was kind of ugly until I met & talked to her, her personality makes her beautiful"!
I think it's a huge cosmic joke that I'm not a lesbian...