He's bullshitting. There's no way he'd know, and if he did work for Rockstar, he wouldn't tell you anyway. And if you could create your own character, there'd have to be several different voice actors for the same thing. It wouldn't work. You'll be able to dress your character differently/customise your character differently, but it is highly (highly, highly) improbable that you will be able to, at the beginning of the game, choose a character to play as.
It could happen, but it sounds daft.