Pochita didn't eat Makima. Denji did. If (Black) Chainsawman had eaten Makima she and the concept of Control/Domination would be forgotten, while the Control Devil would not be able to reincarnate as Nayuta, since it would be erased(/within his stomach).
Denji ate her and digested her normally (well as normal as cannibalism can be). This is probably also the case for other things Denji ate rather than Black CSM. With Power, it's not exactly clear, because at first Denji drunk her blood, then Pochita gave the lingering Power his blood and she emerged from within him. And then either Black CSM or Denji received her blood again, but it's not clear who it was. More likely it was Denji though... Especially if we consider that Denji still remembers Power, and the concept of blood still exists.