Anyone who’s seen Casino Royale (2006) knows the codename theory is horseshit. Bond was Bond before he was a 00. Later, when he resigns from MI6, he’s still Bond. It’s his name.

Same with anyone who’s seen GoldenEye. If Bond was a codename, Trevelyan would be too, and he’d have mentioned that he no longer went by that MI6-given moniker.