Boubacar Kamara and/or Leander Dendoncker generally sat in behind giving him more license to play box-to-box.
True classy 6's are rare, but the very best teams will almost always have one.
Honestly, Bissouma is that player on his day, the idea that he's out of position there is fake news really, he just doesn't play well 2 out of every 3 games.