> If you’re publishing the original book, you’ll be able to use the original title because you’ll be using the name not as a trademark, but as a descriptive term for the book.

You seem to be arguing that it would be descriptive fair use, but the probability of confusion prong of the descriptive fair use test seems likely to be problematic, especially in an active franchise with newer works under the trademark that are actually exclusive to the trademark owner by copyright as well.