It is not impossible to overwinter a nuc anywhere.
I have wintered them through winters that were -50 with wind chill from November to mid February... YES, I lost a couple. lost a couple hives too, but the greater majority of them did survive that NASTY winter..
I agree whole heartedly with everything else...
Nucs are AWESOME for newer beekeepers, they give you an excuse to get into them often, they take more management, and they provide you with resources to keep your production hives in tip top honey making condition.
Winter a nuc JUST like you do a full hive, put SUGAR cakes, or candy board, or Winter patties on the top bars. So those bees HAVE resources to survive the winter. If it was a decently populated nuc, they will surprise you with their ability to survive!