Sure, anybody can make logs of public channels, but there's a difference between "public" as in making a post about it and "public" as in reaching the front page of an established newspaper or recording conversations in a coffee shop. Or not warning people beforehand, as is the standard with e.g. IRC channels.
It sucks and they just keep making it worse while dismissing concerns or just ignoring them: https://github.com/matrix-org/matrix-public-archive/issues/47
It's definitely ban evasion if you tell an organization that you don't want the service that they forced you to use and they still do it anyways, the nuance of it just being a staging server that could have been hidden from the public (or at least used a robots.txt) is irrelevant.