Request vs Require.
"Request" is a preference
"Require" is imperative
SYD operating guidelines require equal noise sharing on the parallel runways. ATC are required to try to balance the movements on both, not simply optimize use of the preferred runway 16R/34L. SYD tower would like to be able to have most international landings on 16R/34L so they can exit west and not need to cross the other active parallel runway, (other than at certain times when there are "departure bursts" when main runway use is weighted in favor of departures) but there are so many other stakeholders ATC is hamstrung by the SYD LTOP (Long Term Operating Plan) rules that try to appease everyone.