So back to the question...😉
The Sydney arrivals are sequenced by ATC to share the runways most evenly & expeditiously. Aircraft up to A330/787 are expected to be able to use 16L/34R and are assigned that runway as & when required.
If that runway is not acceptable for any reason then the captain may "require" (for operational reasons) the much longer 16R/34L with the understanding that the flight may have to endure significant delays in order to be sequenced to that runway.
I've never heard ATC gripe about it; they just make it happen as smoothly as possible when a flight "requires" the long runway. And I've heard flights from all airlines operating the same equipment (eg A330 & 787) either accept the short or "require" the long runway depending upon what each crew determine to be operational necessity. ATC even note, and try to accommodate, each "request" for the long runway as it is made after assigning the short runway to any given flight.
The system works.👍 I hope that answers your question.