True, though whatever his role may be, in an arc; Sanji has never and will never fight an opponent stronger than Zoro's.
So the people who were saying "Zoro fights Queen and Sanji fights Kings, and that's it" weren't just saying that for unpredictability- it was a straight up delusional prediction just stated to satisfy their agenda rather than based on how narrative works lol
Sanji is a harder character to predict no doubt, but a lot of these predictions people make have been absurd; and then these same people go on and shittalk other people who've actually been right so far. One dude thinks Zoro and Sanji will have a combined CoC moment this arc, like, c'mon...