Due to what I believe to be easy and constant Fuel Dumping, China Southern decided (in my opinion) to do 2 things for some TC2-TC3 routes:

1.) Change the COMBINABILITY fare rules to:
END-ON-END COMBINATIONS PERMITTED WITH CZ FARES.
Since they know where CZ fares go, then they can control where to file correct YQ and avoid any loopholes.

2.) Change the way they filed YQ to charge per flight segment making it harder to FD. (If you are an expert hacker you know what I mean.)

Anyone who still thinks airlines do not care about FD is dreaming. Keep FD underground and it might last longer for us.