I wonder what kind of validity checks they have. e.g. a lot of first/last names cannot be paired together because they would belong to different religions/ethnicities. Probably they're sticking with just Anglosaxon names where this is far less of a problem than Middle East/India ones.
There are sources (US SSN and census especially) of first and last name frequency by decade, though not so much first/last pairings. Gender also.