Except allowing people to take up a full two minutes, or however long the allotted time is, discussing unrelated topics deprive people who want to make an on-topic comment of that opportunity.

Let's say the council eventually does schedule a public comment people to discuss Flock. Then anti-abortion activists flood the meeting, and take up all the speaking time ranting about abortion thus preventing anyone from voicing their criticisms of Flock. Is that a good outcome?