Frankly, Ashton's stance on the 'Donald saying "Xigbar"' conversation is quite expected, given his ignorance on pretty much everything he opens his mouth about.
Literally in the FIRST WORLD WE VISIT in KH3, Xigbar shows up. You honestly think the writers aren't going to feel pressured to expose information to newcomers by having Sora, Donald, or Goofy say "Oh no, it's Xigbar!" or something to that effect? That's a 1/3 chance for Donald to say "Xigbar".
That doesn't even factor what dialogue might come after Xigbar LEAVES! "What was Xigbar doing here in Olympus?" "Aw, Sora, don't worry about Xigbar. We'll be fine" "That Xigbar really has it out for you, Sora."
THERE ARE SO MANY MOMENTS WHERE DONALD COULD SAY "XIGBAR".
Frankly I am going to enjoy collecting 500 dollars from you Ashton. It will be very entertaining and the easiest money I ever made.