Is it that different from members of the public asking cops what intentions they have using Flock? Seems like everyone is concerned about privacy, the only difference is that the police is more organised and has more leverage to protect themselves vs (often) fragmented public.

Yes, it is.

A city member coming to your house to ask you about your intentions for something is different from you going to city council meeting. Police, city official, elected officials etc are public servants, they work for the public. The public does not work for public servants and public servants are expected only to ask members of the public their intentions under specific circumstances (common circumstances but specific circumstances - the cops can pull you over for a number of things but they, officially cannot pull you over at random or based on you exercising your 1st amendment rights, etc).