This is subjective fuckaboutery essentially used to police decisions you don't like and endorse decisions you do like. If he was born in Africa and travelled to America then he has a legitimate claim to the phrase 'african-american' - he's met the two criteria required. Whether or not everyone in South Africa has decided to identify as European or not is neither here nor there, we are in a world that lets people identify however they wish with good enough reason.

We don't have a problem with African-American applying to Americans who have never been to Africa (though many in Africa presumably don't agree with this). Some Americans choose not to identify as European-Americans and some bang on about how they're directly descended from the Mayflower passenger list. As a Brit, I don't really want Americans identifying as British-American, we're two different cultures with a huge gulf - but if they chose to and they felt it was important then I couldn't stop them.

The fuckaboutery occurs when we're attempting to police both sides of the argument. If you're prepared to stop Musk being an African-American, then that must also apply to those Americans who have never been to Africa and who have no intention of returning.