I didn't have a big problem with the analysis in Aug: it implictly assumed that Palmer wouldn't play a full season (or even a majority), or, if he did, his numbers would be closer to Stantons than what he did in the six games he did play. If those things they assumed happened, 8-8 would be expected.
Instead -- quite the opposite. Not only has Palmer come back healthy, he took the time to refine his mechanics and footwork. His third year in the offense has elevated his game. Stuff like that is hard to model mathematically.
The inherent problem with models are, they don't represent reality, especially not in the present. They are incomplete guesses based on the past since models don't include all the variables of the universe. The past is not prologue.
The second problem is given that so much was up in the air, and Palmer has always had some great tools and did indeed play great last year, it was kind of funny they would even decide to go down this road an attempt one and assume so much.
One problem compounds with another and leads to being completely and utterly wrong. But they decided to go there. Human error coupled with mathematical error can lead to just about the worst analysis and decisions possible.
It's a tool to see if you missed something out of left field, not a predictor. Sadly, most use it as a shortcut to prediction so they don't have to think. It can take the human brain/creativity element out of decision making, and provides a false sense of confidence which in of itself introduces new opportunities for errors and expands the range of error.
Finally, when wrong, instead of realizing the futility of it to predict, they generally just try to re-tinker with the model, and assume it will be right, until proven wrong once again... rinse and repeat. It's hard to learn from your mistakes when you think the mistake was merely you got a solvable problem slightly wrong, instead of realizing the methodology can't solve it to begin with.