Still, IMHO the OP post is misleading folks into thinking there's a magical GPT-4 that is not the GPT-4 you can also select on ChatGPT, but they are the same models. There's no GPT-4 that's better than ChatGPT's 4. I'm just trying to clear up this confusion for others, and frankly pretty surprised at the harsh downvotes.
There's also no separate ChatGPT API from the regular OpenAI API, I think the phrasing in the OpenAI page is just for convenience. But I'll grant their phrasing makes it canonical.