So My Site migration is a complete PITA with SharePoint 2013. I’m completely over trying to get this thing to migrate.
I’m in the midst of preparing for my migration by recreating my UPS (ala my dance with the UPS style) today and I forgot to set the NetBIOS prior to running the sync. Once you’ve run the intial sync there’s ONLY one way to fix it so that UPS uses the NetBIOS. You need to blow your sync connection away and start with a fresh full sync. Yes, the blog post pertains to SP2010 but it works identically in SP2013. Props to the author for helping me out:
SP2010 User Profile Service Application Setup and NetBIOSDomainNamesEnabled Issues