I also believe that Barry’s long form was legit, and that he was born in Hawaii. The scandal was in his choice to delay releasing it for so long, causing reasonable skepticism about his legitimacy.
why would he do that?
I have some guesses, but they are only that. As far as I can tell, America is not even aware that he DID do that. His missing long form was one of the primary motivators for Certifigate, and he could have provided that long form at any point by making a 10 minute phone call. Year after year after year, and he chose not to make that call.