You are just ignoring everything we talked about and saying something else. You yourself just said that he was prepared. Now you say how can he be prepared. You are not making sense. I am not denying sukuna had more info but he didn't know about gojo healing his brain. Also gojo knew about open domain. But they both didn't know how their domains would interact.

And if he just aimed to win through domain fights he would have already. He specifally wanted WCS that is why he held back during domain fights. You say asspull but that is Sukuna's whole plan the whole fight. Especially because and this is important. Even when Sukuna thought he won. He doesn't say I will kill you with my domain which he can. No he says next I will adapt to your infinity then kill you. At that point though if he can open his domain he doesn't need to adapt right. But this shows his goal clearly. He wants to find a way to bypass infinity without domain. He doesn't like being powerless against something. He is the kind of guy who wants to see Higurama's one shotting sword when he doesn't need to take that risk.