False advertising is illegal in some places (Sony and it’s claims for Vita PS3 remote play, I think, ran into this and they got fined.) but it’s all down to definitions of ‘advertising’ and how that being untrue pans out or is brought court. In this case...no, I don’t think it would pan out. In the Khan case...hmm..well, you would have to define press junkets as advertising (not that hard) and find a group of fans willing to go to court on the fact that they suffered some kind of harm by seeing a film with Khan in (these days, that may not be so hard xD) and then, somehow balance the logical defence of ‘maintaining a plot twist’. It would be a very silly day in court if it ever got going, though again...these days..in some parts of the world...it wouldn’t be a stretch. One for judge Judy.