Hardly, he isn't being deceptive at all, it's that Amazon's categories are so easy to game.
Categories are normal in modern bestseller lists. Take a look at NY Times' Bestseller Page:
http://www.nytimes.com/best-sellers-books/overview.html
There is the Fiction and Non-Fiction list, but besides that are dozens and dozens of categories. And each of the authors in each category is a NY Times Bestselling Author.
Now, the NY Times at least has some gatekeeping done by human beings, Amazon has been easy to game for about as long as they've had bestseller lists. It's the same for all their "best selling" categories, some are just easier than others.