He takes fewer risks. That's why. The few times he does, it's clear he is not as accurate.
Let's not forget, Mangala consistently had some of the highest pass completion rates when he played at City too.
Laporte, generally takes far fewer risks than either Diaz or Stones. This has it's plus and minuses.
On the plus we keep possession consistently. On the minus, we create fewer chances for he attempts and completes fewer line breaking passes.
He used to do far more of this a few years back. Now he is more basic with his possession.