Conte is a random person on the internet ?
See, you complain when i do the smiley, but your comment does exactly the same mister
Let me explain you a few things, so you understand it better.
U-21 teams arent really a reference in several ways. Its basically about raw talent, more then positions and roles. You'll find plenty of top players who have played different roles and positions in the youth sector. Its because the talent is much more important then roles at that point.
You are right about Vidal as an AM at Leverkusen. Yeah, AM. Not trequartista, wich is an entirely different thing. Heynckens used Vidal the same way Conte uses him, but much further on the field. He has the same characteristics and tasks as a box to box player, but he's put far more advanced. This was because of his scoring ability at the edge of the box, and the huge pressure Leverkusen could put on the opponent's defence.
We were talking about trequartista's here. They arent used for pressing and delivering shots from the edge of the box (primarly). The trequartista roams free between attack and midfield, doesnt press at all and is seeking the space there. He is the playmaker that wants to give the trough balls, or holds on to the ball close to the enemy's penalty box.
If you make Vidal or Pogba a trequartista, they are wasted. They may not press, they shouldnt seek for actions. No, they have to roam around and distribute passes to build up the play. Like Pirlo does, but in a far more advanced role. And actively seek trough balls instead of actions themselves. Unless on the counter or when they can have a free shot if they get past their marker.
Think. What is the key difference between Isco, Totti, Pastore... and Vidal, Pirlo ?