Yelp's AI Detection a Big Fail

Yelp says AI-generated reviews are a no-no on its platform, and that it's invested significantly in AI detection. Why then are fake and AI-generated Yelp reviews currently prominent even for businesses with histories of gaining fake Yelp reviews? Sounds like Yelp needs to go back to the drawing board. Special thanks to Pangram Labs for use of its AI detection software.