Originally Posted by Happy

You can search JonNYC's post a few months ago when people ticketed married segment tickets then asked the agent to drop the segment. Note the operative word is, the drop segment has to be done AFTER ticketing. It would not work when trying to drop segment at reservation stage as CX would not confirm it, just like what you have tried. However, JonNYC specifically said, dont do that because AA has warned the agents they are being monitored on the drop segment to break CX married segment booking (after ticketing).

Just go to JonNYC profile and search by his posts - you should be able to find the related posts.
Now keep that in mind the married segment primarily is the attachment of an additional segment before or after the TPAC long haul, but nobody talks about the JFK-YVR-HKG just for the JFK-YVR part.

I dont know exactly how to call this, but here is another example that is how QF control its inventory between LAX and SYD years ago when it still had the JFK-SYD route with a technical stop at LAX. It was a semi secret some of us know that we could find JFK-SYD via LAX, but could not find LAX-SYD. Back then sometimes it was possible to book SYD-JFK via LAX, and then "backtrack" with AA. That is N years ago. Though QF does not have right to fly JFK-LAX stand alone, so it would not be the same as the JFK-YVR CX 5th freedom right. Still, at that time, one could find availability using JFK but wouldn't with LAX.