The grade is poor, but some of the percentages show exactly what Fitz is/does.
He has a low completion percentage when facing pressure, but also has one of the lowest sack percentages on the table. Also, his interception % when facing pressure is middle of the pack compared with other QBs.
This tells me Fitz gets the ball out when pressured without taking a loss and without creating turnovers. He makes the smart play and lives for another down.
I think these numbers show exactly what we thought of Fitz, he's an average QB with great intelligence.