It may have changed but yes usually the mods have to coordinate with Yuletide tech support when they run it. Back when the code was really bad it would affect the entire site. The reason why the support account is on the tagset is for the same reason. Yuletide is so big that it usually uncovers all the bugs and can strain the whole server. You have to remember that of of the unmatchables, they go through and see if they can double assign before reaching out. They would have to do all that over again if they reran.