Are you seriously telling me that two passengers swapping seats is critical to weight and balance? If so that is not a plane I'd want to fly on!
Perhaps the argument that identifying people by seat numbers after a crash on take off is valid but in reality there will be far more important questions to answer and identifying people by DNA is available anyway so not really a valid argument.
Good
PR for the company though. (I identify that as sarcasm as so many people seem to miss it these days!)