Fair enough - I have failed to take the last one or two segments of a paper-ticketed A/DONEx ticket a few times without any problem, including (as mentioned) getting off a LHR-MNL at HKG, and I'm pretty sure that those ticket coupons have had reservations associated with them on some occasions. In the early years these were done via a TA who never had any comeback from the airlines either. More lately direct with airlines and their GSAa.