It's hard to believe that
It's hard to believe that Toyota does not know which VIN is associated with the fuel tank problem after almost 3 years in production. I came from mass production with VQC or Vendor Quality Control where all components can be traced back to the vendors' quality -- this has been practiced in Japan for decades. If it's not components then it's the manufacturing process at fault which is even more unbelievable for a Japanese manufacturer. So it's a design issue. I like Toyota for its quality but I am surprised by this answer.
Is it possible that the problem has been fixed in the latest production but Toyota is holding up information because they do not have a solution for the "old" RAV4 hybrid in the field already?