[SapporoChris]

The assumption being that poor longevity records resulted in fake centenarians. But what if it resulted in missed centenarians?

On the flip side and more seriously. From your link: "Officials have found that hundreds of the missing would be at least 150 years old if still alive." That's just silly, Japan celebrates their oldest on a regular basis. The false claims would and are scrutinized, not just by Japan.

The link is from 2010. My point being yes, the absurd claims are investigated and debunked. It's a known problem.