So, Google has done this before. They do omething similar with dislikes on YouTube. They aren't doing it manually. When a bunch of pissed off assholes brigade an app and flip a bunch of five star reviews to one star reviews based on one policy change, that's generally not something that Google want to have too trong of an effect. If negative reviews continue steadily over time, they'll pile up.

I recommended this on Matrix. It really was necessary. The site admins are in favor of vaccine misinformation and extreme fearmongering to the point of hostility towards science in general.