it just would make more sense to make an X shaped scar with 2 swords. especially while being an 2 sword style user.
If we look at scar then left arm of its longer while the right arm is more wider.
Now, himura kenshin infamous X shaped scar was also similar to it which was done separately two form x shape.
Now, I do admit that kenshin scar is nothing in front of Kaido scar and way more easy to be made separately but what I am trying to say is Oda could be inspired by it and can make oden give two scars to Kaido separately which became X shape.