Lol isnt that the truth?? Andrew Whitworth is a top LT in the league and never makes the pro bowl. This is part biased but even ESPN says the same thing.
To the OP, I've always thought it was based on number of pancakes as well as rushing/passing yards (which one depends on their season goals). This is just my belief but I think that's how it comes out. Pancakes + goals met + actual yardage above the goals.
I would love for someone to do the research on each position though. I'm personally too lazy and impatient to try it lol.