It's a subtle distinction; the `optin` parameter has nothing to do with a valid API key in context of this function, it just controls if you want to skip subscription confirmation. The value that is normally passed in, however, does depend on whether the API key was valid or not, but this function couldn't care less about API keys being valid.

It's not a terribly important distinction in the scheme of things, but it caused confusion for me because I was wondering why this method depended on the API key, and didn't know the effect of the parameter. Either way, your edit looks fine to me. :D