Which is appropriate considering Killer is both damaged and tired a lot and did not get a regenerative drug like Zoro did. Killer just comes from fighting two top tiers and goes on to fight an opponent who normally would be a mid to high diff for him in the first place.
Zoro will beat a Y1C after giving it all vs two Yonkou at reduced state ( how much we will see) implying he is beyond Y1C, whereas Sanji is almost at peak state and will beat a Y2C.
Even if we assume Queen and King are almost equal ( which is not remotely a given considering the other crews), the preexisting conditions are different.