There's no need to go on a hunt of meta commentary. Everything you need is in the manga:
That is a page of Kuro literally running between everyone. Has he not become invisible? Has he not disappeared?
After that, claiming "Sanji's the first to disappear through speed" becomes "Sanji's the first to disappear through speed if I ignore the times it's happened before". It's common sense that it depends on the opponent.
While Shanks would immediately behead Kuro on that very first panel, East Blue Nami wonders if it's all over because she can't even perceive Kuro.
Same difference between Shanks and Queen if Sanji speeds up before them.