I wasn't there to confirm the situation, but I have heard the same. I guess if you went back to the dealer a couple times and made a scene, I've heard some would put round tops on it to appease an unhappy customer.
All that said, a true stock 73 should have flat tops, as should a 74. I can deal with an early 73 having a set of later design flat tops (since that update is documented in Nissan's literature), but I would start subtracting points for any round top on a 73 or 74 in a stock class.
Flat Is Phat!! (I didn't make it up... I'm just promoting it.)