Agreed. But look at it from a different anfkw, Dihno and Delph have energy for days, they will help the defense regardless of where ther are in the middle. Yaya helps most only if it is in fact his job, which it was at WHU and he did it admirably. Kouyate blow by notwithstanding.
Also he gets more space to orchestrate, and have 2 CMs ahead of him who like making runs in Delph and Dihno.
Yaya on the other hand doesn't like making off the ball runs, would rather be the passer.
From what I've seen, Yaya at the bottom of that triangle is best.