You don’t have to be able to read music to be a musical genius. You can learn to read music in about an hour.
If they're geniuses, and it only takes an hour to learn, why didn't they do it? Don't get me wrong, I love the Beatles, Stones, etc. but to call them genius is a bit delusional. Just my opinion, of course.
IMHO, it’s much harder to play an instrument when you CAN’T read music!