Perhaps the horns were a red herring, like the Lotus, 'four second a lap' diff, which turned out to be enhancing underbody airflow.
A mclaren smokescreen to hide a real advantage they had found?
Murphy's 9th Law of Technology:
Tell a man there are 300 million stars in the universe and he'll believe you. Tell him a bench has wet paint on it and he'll have to touch to be sure.