As weird as things get, they just get weirder. I never really thought I would hear the phrase "outed as a fake black person" ... it is absurd, from every angle.
I believe this goes on more than anyone knows.
Especially if a person is one "race or ethnicity" growing up and living around people of a "different race or ethnicity." People like to fit in.
I just found another famous example, this one a musician in the 1900's: