It's an old in-joke based on a comment I read somewhere in some fan forum once, about the idea of writing a story entirely based on overcoming the social barriers existing between Raoul and Christine without any additional Erik-complications, to which someone else replied 'but then it wouldn't be The Phantom of the Opera but The Vicomte of the Opera' ;-p

In fact by the time I encountered that particular long-dead discussion I'd already written Count Philippe Takes a Hand, which does precisely that...