Nothing to do with zones anymore. The requirement is that the jaw needs to be less than the shortest flight segment.
So LHR-AUH // DXB-LHR is fine, as AUH-DXB is shorter.
LHR-AUH // JFK-LHR is not, as AUH-JFK is longer.
Interesting, is that true for any open-jaw and not related to the 241 ?
(I was somewhat surprised that LHR-JNB / HKG-LHR was cheap, but then disappointed that LHR-JNB / NRT-LHR didn't and this would explain it - I am joining up an AONE4 which I will travel in two portions)