Sorry I'm late to the party.
If I were to venture a guess, based on the data published on the states website, I'd have to say it's because of the significantly higher derivate count in Fiji.
I mean I was looking into the DV data published on their site and it's pretty obvious why. The Fiji derivatives : applicant ratio seems to be significantly higher than Oz, NZ and my money is on it being at least two - three derivatives per Fiji applicant, in the past couple of years (stats not published by them yet)
Australia and NZ has much lesser than Fiji, in that front (for an average NZ, Oz applicant, We've got ~0.5 derivative count, implying lots of single applicants in these two countries)
Since the total Fiji derivatives : applicants ratio has been consistently much more than the ratios of Oz, NZ over the years, the stats never go current in the bulletin in the past few years, since the Oz, NZ allocated quota is getting eaten up at the interview stage, by the derivatives in one area of those that has lower CN
And because of this very reason, higher CN of Oz, NZ never gets a chance. So the applicants of these two countries may technically be getting selected and alloted CN, but never get their 2NL, because visas run out, by the time it gets to the higher CN (unlike the past when it almost always goes current)
This is my theory based on the published data
Thoughts?