The intention is for parameters like 'minrate' to be set in DNF so that it may select to change mirrors... if rates aren't sustained.
If, for example, the download speed falls lower than 10Mbit over thirty seconds, it can pivot. Both parts of the formula are configurable - time period/rate.
In True Stallman spirit, they want the systems to work on your behalf, not the other way around. Keep many mirrors so that the client can effectively get the best one.
Sometimes 'best' means the fastest or most capable to meet the requested rates, other times... simply available. Unless you're running the mirror you probably don't want to limit yourself.
To that end... one can point networks of clients at specific mirrors using netblocks, but this is more for campus administrators:
https://fedoraproject.org/wiki/Infrastructure/MirrorManager#...
If still committed to one mirror, there is nothing stopping the replacement of 'metalink' lines in the repo definitions with 'baseurl'. That takes out MirrorManager