A few things to note. First, every case number does not actually exist between those numbers (see “holes” discussions on britsimon’s website if you’re not aware of this). Second, not all OC cases interview at Sydney. Apart from NZ, the bulk of OC cases are usually Fiji. I believe we don’t have the DV26 breakdown yet but as an illustration, last year within OC the breakdown was NZ 302, Australia 894 and Fiji 2359 (plus much smaller others). These are #s of selectees not cases, but you can see the relative proportions (and they are usually fairly similar year to year), in other words, the cases going through Sydney are roughly only a quarter of OC cases assuming most interview in their home country. Third, unless something has changed,
@Xarthisius will indeed have (though i believe not yet) information about which cases get interviewed.
But xarthisius’s point still stands, that once numbers get current the exact order has less relevance.