You never seen Matuidi play? Or not grasping tactics or how to utilize specific player qualities much. Just because you play higher up doesnt necessarily mean you arent defending more. First of all I'm not keen on the idea of Pjanic as regista full time since he doesnt seem to move as one, but how Allegri invisions the role, Pjanic is more suitful for it then most we have (you said cerebral CM, but nothing is more cerebral midfield role then having this kind of player as regista), and Matuidi if you mean DM as in holding midfield is NOT possible. He cant, neither tactically (there is a reason Pogba was used as DM in Euros...), technically, not remotely close to how to best use him. He is very physical, quick engine of a player who needs to run into space and cover ground, hardworking box to box runner, he can do defensive work more that way then as traditional holding DM.
Who also says just because Matuidi plays higher up/to the side, he will set up the offense? lol. He will do most of his work off the ball and play 1-2s or get into box offensively, he will rarely hold onto the ball for long (lacks the technique) so why do you think he will get the ball from Pjanic to set up the offense? It will be the reverse, Matuidi will play it simple and mainly quickly give it to attackers or Pjanic to set up the offense.
Maybe its you who needs to wake up and not the Allegri who earns millions to tactically solve things for these players?
You know Pjanic well since he is a cerebral type of technical playmaker (tho not all around vision type, more of quickly solve with individual plays type), but you seriously need to watch a highlight of an average Matuidi game and how he operates to get a sense of him before calling him a holding DM type:
He is so crappy technically

No way anyone should want him to be in holding position to receive the ball further down.