I'm 99% sure that "Unfired" is the proper term for pottery that has not yet been put in the kiln. "Burnt" refers to things which are consumed or destroyed by heat and flame, which is not what happens to a Pot.
This has been bugging me for a while, and I couldn't find any threads about this. Sure it's minor and doesn't affect gameplay, but if there are errors in names and text, they should be pointed out.