Well, I said that this is where I thought that my mom heard it, I know that he didn't come up with it himself, and I didn't realize that Michelle Obama had been famous forever.
It is untrue, and racist itself to suggest that African Americans are more athletic generally than other races, and ironically enough, those that identify as African American are the demographic least likely to believe this myth, according to polls. I say "self-identified", because "race" isn't actually a scientific classification, based on genetics, or relatedness, but it a superficial, archaic prejudice infused cultural artifact. There are some populations in African more closely genetically related to Europeans than they are to other groups in African, yet they'd all be considered "African", and if living in American "black", or "African American". There are a number of reasons why "races" are vague, unscientific classification, more reducible to culture and geography than genes, but I think that's sufficient.
I don't deny that it has something to do with racism as well, it almost certainly was. I was more just focusing on my own experiences, and people around me, and why I thought that they would find this attention grabbing, and relevant at this time, rather than forever ago.
I don't like how my family tends to be all respectful, and seemingly supportive to my face and about me, but then when talking about someone like Jenner, they are quite the opposite, refusing to acknowledge her identity, criticizing her looks, and bringing up this Michelle Obama thing... the passive aggression I deal with... lol.
I just saw something of a silver lining to the topic of Michelle, in that they were basically point blank telling me that they can't clock trans people, and are perhaps just as likely to accuse a cis-person as a trans person, though, at the same time, feel like it's my fault that they're even looking, regardless of a lack of actual discernment.