@Tatsuya-Kai that seems to be a detail corrected in the tanks or possibly was never correct in the first place, I am not sure.
Sullivan is squatting at Tet rank according to the uploaded ch 23 by Desu Vult's work: Levi expressly says he should give up resisting and ascend to Yodh already; that's consistent with how the anime depicts the conversation. He's doing it so he can't be forced to become the next demon king by the 13 Crowns or by Levi and Belial by virtue of not being the requisite rank even if his power and influence is unquestionably within that tier. Why he's so resistant to becoming the next Demon King, even if he decided to do nothing but maintain Delkira's current status quo, we've yet to be given that insight beyond that little talk he has with Iruma about the ever-shifting nature of the demon world, where he only said he didn't think he had it in him.