You're reading the data wrong.
Fitz, on average, would get rid of the ball in 2.5 secs. Yes thats the 4th fastest time. That stat alone tells you nothing. A QB could get rid of the ball very fast for a variety of reasons. Maybe they run an uptempo, quick strike offense. That doesn't mean the offensive line can't block. If you read on, you see that average time to sack tells you more. The Bills average sack time was 3.61 seconds, meaning FItz had a full second more, on average, to get rid of the ball. Meaning the line was holding their blocks longer than required for him to get rid of the ball.
Look at the other end of the spectrum. Roethisberger, on average gets rid of the ball in 2.76 secs, whereas his line, when its a sack only, holds there block for 2.43 seconds, on average. They aren't holding they're blocks long enough.