No that is factually untrue, sanji fighting king makes sense because of his connection to the momo plotline and because that is where sanji is headed right now, furthermore king already tried to kill sanji once so no its not superficial, the people wanting zoro vs king are only providing superficial reasons like the sword and second strongest narrative which has been non existent in the post time skip, also they want zoro to fight king to rub it in the sanji fans faces and say that not only did zoro fight 2 yonkos but he even beat the strongest enemy down below...…like it or not its the truth.
"The Momo plotline"
Literally all the beast pirates who are still loyal to Kaido want Momo dead, it's not like King specifically is hunting him relentlessly, he just realized Momo is basically the figurehead of the alliance so he took the initiative to tell the rest of the crew to go and kill Momo.
Hell, by that logic, we might as well say King vs Yamato is guaranteed since she's the one currently protecting Momo.
Seriously we have so many characters that want to either kill or protect Momo in the island, Jack or Queen could somehow run into Momo first, Yamato, the scabbards and pretty much all of the alliance want to protect him.
"He already tried killing Sanji once"
Yet he immediately went back to do other things, without ever acknowledging Sanji again. Sanji hasn't expressed anything regarding King either.
With the situation we're at right now neither Sanji nor Zoro have some guaranteed 1v1 opponent that's been foreshadowed, it all depends on the situation they end up in.