Disclaimer: I am a dinosaur. Contractors should know enough about codes to perform their construction in compliance, but in my opinion contractors should stay out of the design and leave it to the designers. As an architect who devoted considerable effort to producing designs that complied with codes, I hated contractors who whispered to owners that this or that "doesn't meet code" -- without ever being able to quote a single sentence from any code book to support their allegations.
If your contractor thinks that door violates some provision of some code, he should be able to show you the code or tell you the code and the section number so you can look it up and verify. Otherwise, he should shut up and sharpen his pencil. He brought it up, not you. If he's not willing to dig into the code enough to support his statement -- you may not want him to build your house. IMHO you're likely to encounter other problems.