It feels different when the book sequel came out after the movie. Like, wouldn’t that fall into the same category, but from the author chasing the same story again?

The Devil Wears Prada is a complete story. You can make sequels to anything, but there isn’t anything that suggests that these characters would conflict again based on the conclusions of their arcs.

It’s similar to the new Hunger Games properties. Yes, they’re based on books as well, but those books were made because of the popularity of the movies and a drive to tell more of the story in order to get more money, rather than narrative that was needed to tell the complete story.