All the stats adjust for team talent. So that they isolate the individual person's performance.

This data would imply that the best QB's (Brees was 3.1, Rodgers was 3.0) are over 3x as important as the best HCs (Reid was 0.9, Payton was 0.8).

It also implies the best non-QBs are equal to the best HCs. Brown was 0.9, other players were 0.6-0.9 per year.

Add this all up, and Frank is largely correct that the NFL is 90% about roster talent, and 10% about the Coaching.

Of note, "wins over expected talent" and "wins above replacement" are roughly equal. Wins above expected talent looks at how many wins you got out of your team, as a comparison to how many the team would've gotten with a replacement level coach.

Finally, no this data is not perfect. But it is dirrectionally correct, and is largely backed up by reports/articles out of Sumner Sports and others.

Head Coach Wins Over Expected