
Is it? Have you checked 2007 Port Adelaide's finals form heading into GF day? They just won a prelim by 87 points, which was the very most recent data point.
From this angle, I can understand how you have them well ahead of 2011 Collingwood just like the rest of the football world.
One exception does not mean that finals form is not the best guide to how good a GF team is.
You would have to show which of the other possible guides(h&a wins, previous & future years performance, AA selections etc is a better guide.) None of them are.