This can bite DL back, and be a further drain on already abysmal availability.

If N is available on A-B-C, but not on A-B, what is stopping one to book A-B-C but only fly A-B and "miss" the "connecting" flight B-C? (Of course, if one does that frequently, then the account may be audited and closed and all SM lost, but I doubt that doing so once or twice would be problematic...though it could be as per the CoC, if it is strictly enforced and applied.)