So while what you've said is true, do understand that Atletico don't use a DM. They play 4 across the midfield and the 2 central midfielders help defend and attack. They are plain central midfielders who do both jobs.
Saul is a ball winner and not only that but I made a thread on here when he went out on loan before making a breakthrough at Atletico...
https://www.redcafe.net/threads/saúl-Ñíguez.375742/
He played 20 games as a DM for Rayo Vallecano in 13/14
and not only that but he also played CB for 13 other games.
It was these defensive skills that made me think Saul was going to make it at Atletico at a time when everyone was hyping up Oliver Torres to be a big player in Spain. Oliver just attacked, Saul was good on the ball but also had a defensive side to his game and Simeone likes to pack midfield with competitive players.