They really have, because that's the sole reason they exist.
It's like arguing that a oppressive totalitarian regime doesn't have to oppress their citizens.
> (...) they can be tools to communicate to good-faith actors that they will be welcome and safe.
CoCs aren't welcoming letters. CoCs are designed with the express purpose of letting you know that you will be punished if you do or say anything that the leader's deem unacceptable, and to be used as the basis for persecuting and punishing you if you still fail to fall in line and comply with the leadership's will.
Hell, you don't need to communicate to anyone that they can and will be safe. Either that's already implied, or means nothing if you don't plan to act on it. In fact, it's patently wrong that the goal is safety. It is not. The goal is compliance and submissiveness.