Given that he knows that we know what it is or at least what it will make since long ago ie, creating a "one pièce" of sea, by the help of the ancient weapons.
And given the fact that knowing oda, he would rather give a worse explanation to it just for deceiving the fanbase in their théories as he usually do.
And given the fact that knowing oda, he would rather give a worse explanation to it just for deceiving the fanbase in their théories as he usually do.