My guess is that he thinks SQL is an app or implementation like MS-SQL. It would be pretty surprising if the government didn’t use SQL as in relational databases, but if it doesn’t it’s even more unlikely that he understands even the first part over whether having duplicate SS numbers is in any way unexpected or unreasonable. Most likely one of the junior devs somewhere along the lines misunderstood a query and said something uninformed and mocking, and he took that as a good dig to toss into a tweet.