I actually can't see it as a sequel to any version but especially not to the film. "The true feelings of Christine and the Phantom are revealed in LND!" I'm a die-hard E/C shipper but still I genuinely react with: Fuck no. Forgive me the strong phrasing but I upendo logic very much as well as the depth of their relationship which LND completely shits over.
Then someone comes saying LND isn't a sequel to the film but to ALW's PotO. But also that the film and the stage play are exactly the same thing. (Contradicting much?) Well, officially they are not exactly the same thing: