I likely wouldn’t vote for an autobiography in any form, but I don’t think it’s outside the limits of what is ‘nonfiction’ if it’s just a writing style choice and not mixing truth and fiction.
I read a book like that but it was about a Sexy Sempai scolding a self-insert MC into learning about databases. I would not consider those types of books to be nonfiction. If Natively would let me add it (sadly not on Amazon, but it is on Bookwalker!) I’d probably add it as a textbook.