It does tell something about a user.
However, it uses information that is already there, it’s not storing extra data. It’s not more or less GDPR-friendly than the other activity of a user on a forum. And the data is averaged, it does not give away concrete data points.
The whole idea about the plugin is to make the information available between users, so making it available to staff only is outside of what I think would be meaningful use. I would accept a PR.