The weighting and direction of the pass in particular. He knows when he needs to drill it into someone's feet, when to play it ahead of someone, when to float it etc. Really intelligent footballer.
There's certain instances when you have the ball just over the half way line and there's a central option as well as a wide option/sideways. Xhaka and Elneny will make the central pass 5-10% of the times, Ceballos maybe 10-20% of the time. Partey makes it around 40-60% of the time which allows Laca to get it wide late in the move when the winger/fullbacks have space. Makes a big difference.