I think what you might be referring to is that a few years ago, people were given the chance to join FTA in Adelaide as instructors. On completing the instructor course, they were given a CX seniority number. They had to complete a certain number of months working in ADL (maybe 2.5 years?) then they come straight to HKG as DESO with the seniority number they had 2.5 years ago.
So in that case they would upgrade earlier than a DESO who arrived in HKG on the same day.