Some of the names are probably real. But anyone can purchase a membership online and I don't believe any special steps are done to verify accuracy.
That said, when a player goes to an event, they should have their ID and USCF ID checked to verify they match. I know that does not always get done but it should.
I am confused about some of the odd names that I have found on the USCF player database. Here are a few
King Arthur Curry- Did he enter this as a joke??
Justin "GM" Hull- Not a GM-this is his nickname in St Louis
Dylan Challenger- Is Challenger even a last name??
Michael Challenger- He may have followed his brother's joke
Nicolas De "T" Checa- See below
Please note Nicolas is an IM- and his last name is just "Checa." Did someone screw up when registering him?