For the longest time, the Fedora Project has included a baseurl= line in its configs as an alternative to the basic metalink= line. EPEL has followed along, and I expect a lot of users have some sort of sed/awk/ed script which looks for a #baseurl and does something with it.
The upstream configs in Fedora's repo files are changing to only have the metalink= line in them, and a couple of Pull Requests to make the changes to the EPEL config files have been placed.