I know what caused mine. And it was not electricity. It was exposure to a strong subsonic sound for an hour and a half. I have read about a lot of different causes. My father had malaria and after taking quinine for it, had tinnitus for the rest of his life.
Mine was 32 hours flying in a cargo jet cargo hole without any protection while I was in the service. I have had tinnitus ever since.
I did a little looking and I found that the author is indeed apparently just an author. Not a medical professional. Not a medical scientist. He even founded an organization that opposes electricity basically. So it seems to me he has a bit of an axe to grind of his own making.
For me: loud rock music in headphones and possibly ototoxic drugs back in the day from surgery as a young child.