Transformers used with Class 2 or 3 circuits are exempt from the rules of Article 450 by 450.1 exception #4. Class 2 and 3 circuits are in parts I and III of Article 725. Section 725.51 covers the wiring on the supply side of the transformer. Did you violate something here? What do the installation instruction say about mounting this transformer? Is there a problem with excessive heat in this attic? Is your transformer marked with Class 2 or 3? Is the location of the cables or transformer subject to damage?
If the inspector cannot cite a specific code section you have violated, then there probably is not a violation.
