Cmon he just doesn't know the fluff aswell as you do.
Logically speaking though, there is no reason why CSM don't have access to a most loyalist stuff. (Forge world can be conquered, STCs can be stollen) This has been discussed over and over again on so many boards. Not all csm are blood crazed zerkers or mutants some are relatively new converts like Astral Claws. No reason why they shouldn't have any of the SM units or Formations.