It is on by default, but can be disabled in your repo config: https://dnf.readthedocs.io/en/latest/conf_ref.html

The feature works by adding a flag to one random http request to a fedora repo every week. Fedora then aggregates the http logs that have been flagged to derive their metrics. You can opt out of sending the flag, but if you’re querying fedora repos then you still end up in their http log.