I found that thread when I searched. It's from 2012. By the looks of it this was already implemented and outdated info for the current releases, as the options for finding the fastest source is present in the updater. If you read the more recent posts in that thread you'll see that people still have trouble with certain sources.
Either way, it does not change the URL's on the "Other" tab, these were still pointing to debian.linuxmint.com, at the time an extremely slow source.
Last edited by inflatablemouse on Mon Nov 11, 2013 7:54 am, edited 1 time in total.