There are exactly zero ASA-approved Thunder Advance models.
If it has a stamp, it's an old ball that's since been moved to the non-approved list. If it doesn't have a stamp, it's never been ASA approved. Irishmafia is pretending there's a world where Dudley might one day, hypothetically release a super-secret non-multilayer Thunder Advance (even though the whole idea behind the Advance line is multilayer...), in the process recycling the name to make saying "Thunder Advances aren't approved" technically incorrect. He's going to tell you that widely understood colloquially phrasings are entirely wrong.