Sorry, but it's not. If the business cabin is full and an über-Ulti ( or worse, two of them! ) coming up exercising their booking guarantee someone has be to bumped. If you deny that somebody would have to be bumped then your "guarantee" is not worth much. Your guarantee means that i would get a seat on a flight that is already zeroed out in J, zero seats available. That makes it easier for airlines with a first class like LH by just op-up you to F, but what is KL supposed to do when YOU show up at the gate at an already full flight?