So, if I understand correctly, for the protection to exist, all flights have to be linked and through checked-in? I.e. I just had a recent flight, BOS-DFW-HKG on an AA ticket and HKG-MLE ticketed on BA but on CX metal. For protection I would somehow have to check in for all flights at BOS? Is it even possible for AA to check me in on a BA ticketed CX flight, and issue a boarding pass?!

How would one go about linking the two tickets? Last time I talked to AA they couldn't even view tickets with a BA record locator.