Wow, edo, that's a very surprising set of numbers and, taken at face value, lays a lot of the room for correction at Watson's feet.
But as I think about what might have skewed those numbers, I wonder how much Watson's high 3.2 seconds holding the ball was pushed up by a lot of VERY high "holding on" plays with Watson holding and running around and holding and running around some more. I'm know not saying that well.
Okay, try this: if the statistician took out those extremely long plays that he was running around because the blocking broke down, what would Watson's "holding on" number be? Does this kind of stat penalize Watson for being an escape artist? Probably.
Of course, no matter how that would have changed his numbers for purposes of this stat, it's obvious that he should get rid of the ball faster. Some of that's on his recognition skills, some of that's on the receivers, and some of that is on the play design / play calling, as TK said.