That is one of the issues with the old cohort ID system, in particular: You could be placed in a group that is particularly concerning for targeting purposes an

That is one of the issues with the old cohort ID system, in particular: You could be placed in a group that is particularly concerning for targeting purposes and not even know it, because everything was opaque. You just see a weird cohort identifier, but it might inadvertently discriminate against you in some way. This attempts to solve this by limiting it to a much more limited set of topic groups that are presumably plaintext-readable, and it sounds like the option to remove yourself from ones that are incorrect may also be considered. That being said, I'm happy to use a web browser that doesn't consider better ad targeting a reason to implement features.