Originally Posted by
bcnfish
As it's not possible to have a mixed F/J booking paying the F mileage rate it's actually beneficial to be able to mix an actual F (O class) seat with a connecting flight in J (mistakenly showing as O class).
But these "mistakenly-shown-as-O-class" flights are actually the ECONOMY flights, not the business class ones. There's no benefit in booking one of these and, even if you do, I suspect bookings will be cancelled when they realise the mistake.