Qantas Reward Booking - availability confusion

[GCflyer]

Looking at making a one way reward booking from Brisbane to Hong Kong for 2 pax flying Cathay Pacific.

I'm a bit confused as on my required date no availability is showing on flight CX150, however if I try to book say Brisbane to Seoul on the same day, rewards seats are available....with the first leg to Hong Kong being on CX150, the exact seats that I want, before boarding a different CX flight to Seoul for the second leg 5 hours later....

Just wondering if there is a reason for this and would ringing Qantas help? I've noticed it happening on a few different flight reward search engines over the years.

Thanks in advance for anyone who can shed some light on this

 

[jetpack]

Married segments. It won't help you but the people who actually want to go to Seoul will be happy this rule exists.

Edit: Married segments - what does this mean

 

[GCflyer]

Thanks, read up on them....although i'll never fully understand the mystery of some of these booking engines and intricacies like why it sometimes costs less to fly an extra leg.