I wrote to them asking last year asking why all seats on the market weren't tested and how they selected the seats they did test. A rep from VicRoads called me, she said that because they only test annually (well more like bi-annually ) If seats aren't released for sale in time for their intake they don't make that round of testing. So there isn't really any rhyme, reason or selection process. That's the best I could get out of them.

This years, or last years really, took so long and were delayed so long, I think they could have added a few more. But that's just me lol

It's a good guide, but it really is lacking in the number of seats included and needs more regular testing to keep up with the release of seats. By the time the results are out, they're quite outdated.