The way I read it was:

When you are programming against an API, you are using the interface. When you use an interface, you are a user. You are even the expected User from the API designers perspective. You are that API designers customer. In your job as the User of that API, you also have different customers you serve. But that doesn't mean you are no longer a User of the API. Because you are the user in this case, using an API, then that must mean your going to have a User Experience with that User Interface that just happens to be in a API.