You could complete every ball and throw tds but if you re checking everything down and you have guys open for chunk plays you get penalized which is way more likely why Cam was so low in week 1. If he dumps off a pass and the wr or back runs 50 yarda after the catch an analyst judges who gets credit for what. Its also why Zach in 2020 played the worst schedule in BYU history but put up historical PFF. He basically executed on chunk plays as much as you could.
He wasnt penalized for playing a bad schedule because he took full advantage. Dax Milne same story. He played some really bad teams but wasnt penalized because he won his matchups almost every play with tons of big play credit.

Ultimately