But McCarthy meant that he had 50+ concurrent consistently-actively-pursued hobbies/passions.
Which is something that's possible... if you have a lot of time on your hands, and you never allow anything into your life that drains you mentally so much that doing it kills your motivation to do anything else for the rest of the day. (Which IMHO is really only an option for people who are either retired, "independently wealthy", or being homeschooled.)
Still think he has ADHD?
I myself paint watercolor and oil, am learning violin, joined a sailboat race team, am writing a book, started my own successful business that earns my living, lift weights, read 35 books, hiked 1000 miles of the AT, and became a volunteer firefighter, all this year. I'm currently designing a cabin I want to build. I'm having a blast. I definitely don't do as much with any of these hobbies as someone who only has one hobby, but I don't care, give me variety!
> As a child, McCarthy saw no value in school, preferring to pursue his own interests. He described a moment when his teacher asked the class about their hobbies. McCarthy answered eagerly, as he later said, "I was the only one with any hobbies and I had every hobby there was ... name anything, no matter how esoteric. I could have given everyone a hobby and still had 40 or 50 to take home."[15]