It is not at all unusual for cities, towns, states to have their own amendments to one of the national code sets. Now, whether the plumber is correct or not, I cannot tell you - you'd have to check with the local permitting/inspector's office or find it online.
For example, in MA, any plumbing fixture has to have been tested and approved before it can legally be installed. They have their own website where you can check. There is an appeal process from what I understand. Funny thing is you can buy stuff not on the list, but it is technically illegal to install it.