Yeah, but if I identify as a queen of England, I'm simply delusional. I don't get what's so unusually interesting about it. Psychiatry has been dealing with delusions for hundreds of years.
Whether you're the Queen of England is a factoid. It can be either right or wrong.
Whether you're sexually attracted to men or women is entirely subjective and not mutually exclusive. You can have a preference, which is most likely what you identify as, but you won't find the other sex entirely sexually unattractive as a result of that.
The difference between madness and experiment is the method and results.
People do not have to be consistent. Three follow up study could try to determine how they identify themselves later and what kind of sex life these people have. The study is probably underpowered to detect any mental issue if any exists whatsoever.