Deceptive plays and formations are such a big part of NFL football that it’s hard to know exactly what was planned on any particular play. What looks like a mistake might have been exactly what the coach ordered.
In mid-December, Chip Kelly dismissed Pro Football Focus’ ratings for that reason:
...how can they grade an offensive lineman when they don’t know what the play is? I’ve had it before [where they said that] our left tackle gave up a sack. He didn’t give up a sack because the guy slanted in the ‘B’ gap.