It's an interesting explanation. (That gay men pay more attention to their appearance than straight men because they want to be attractive to men rather than women, and men both gay and straight are more visually oriented than women.)
This theory would predict that gay women would pay much less attention to their own appearance than straight women do (since the women they want to attract care less about looks than men do).
Do you think that's the case?
There are exceptions, where they just go for "comfy", however.
Men over 40 do not need to pay any attention to their appearance, grooming etc. They just need to not wear a wedding ring. (Ask me how I know...)
But they would absolutely NOT tolerate their partner actually spend more time fussing about his appearance than them. Instant ick. Feminine behaviour.