The blue zone debunking was done by somebody outside of this field of study. The actual researchers who did the on the ground work to verify ages aren't so foolish as to just blanket ignore this sort of thing. Verification is more complex than "ask Bob how old he is and write it down."
"Blue zones as health miracle" is overstated. "Blue zones as simple fraud" is overstated.
>Okinawa in Japan is one of these zones. There was a Japanese government review in 2010, which found that 82% of the people aged over 100 in Japan turned out to be dead. The secret to living to 110 was, don’t register your death. (conversation article)
None of the blue zones from the actual research are cities this large. And the researchers that identified the blue zones did not get their data from government census information.
https://en.wikipedia.org/wiki/Okinawa_Centenarian_Study