No, that's true, it's indeed the code to unlock Ramjet. The one you can use without a code is Dirge.
What he was referring to as untrue was the statement that Ramjet is multiplayer only. Once he's unlocked by code input, he's available for use any time you can use any other Decepticon. I.e., in the Decepticon version, you can use him in story mode, as stated in the post.