Morata-Tevez was actually the perfect partnership.It was clear to see why he flourished more in his 1st season.Tevez could play with his back to goal,just like Mandzukic this yr,holding up the ball,laying out the passes so players like Morata can run into space.Morata enjoyed the supporting role more imo.
In contrast,Morata-Dybala hasnt been particularly flourishing because of the same reason.He cant play with his back to goal all that well.
Its no surprise Allegri sees him as more of a support striker.