Is this years prospectus out already?In the prospectus they go into further detail and compare players against those of a similar age (and position) to determine where they sit in the scope of the playing group. There are overall all encompassing comparisons/rankings, but they also go deeper to give a better understanding. Rather than just saying, and I'm paraphrasing here without any stats attached, 'Josh Kelly is heaps better than Sam Petrevski-Seton' they also add something along the lines of 'But SPS is waaaaaay better than the average 19-20 year old midfielder'.
As far as I'm aware the AFL 'Player Rankings' are a little different to CD's evaluations in that they're more about sheer output (ie sum or av of a huge amount of complex game stats) rather than continuous/sustained output of more basic stats over several seasons which the AFL rankings really favours, in the same way that the AFL's Fantasy numbers don't quite relate to CD's SC numbers.
I agree with pretty much everything you said here, I was just pointing out that whilst they do comparisons and compare players of same age and position, the actual ranking that has placed our list last doesn't take age into account and therefore it is not surprising that we would be ranked last. The Champion Data rankings definitely seem to use the 40 game method that the AFL rankings do, I wouldn't be surprised if they were the same.