I think the more appropriate analogy is "shit filter."

I really appreciate project managers that know when the customer is full of shit and can filter that out from our discussions, keeping me and my colleagues focused on the things that actually matter.

On the other hand, when I did front-end work, I was really annoyed that the management would keep the secrets of customer feedback to themselves and only let through the things that aligned with their own "vision." Honest feedback and actual usability testing never seemed to be something that the higher-ups cared about; they simply wanted to go through the motions. I wished they could just let some of this information through.