IDK, I kind of have a hard time believing this. Because like, when you look at an average straight person, the majority of them have to go through several dates, and several relationships before they find someone they click with. The likelihood that someone who isn't all that attracted to the opposite sex would just happen to find the right guy right off the bat at the frequency that they do (because there's a lot of people who claim to be "lesbians with exceptions") and the time that they do (seems to happen a lot in the late 20s early 30s) when normal straight people have trouble doing this, make me believe that they're not being honest about their dating history. And I personally have seen many "lesbians with exceptions" who regularly dated men in the past. Maybe some of these people were clueless bisexuals who really did have no idea that they were attracted to men until ~that one special~ guy showed up but for a lot them I think they're just people lying about their sexuality.