OpenAI is treating GPT as a "foundational model". They spend time training the foundational model, then build on top of that. GPT was published may 2020. GPT 3.

OpenAI is treating GPT as a "foundational model". They spend time training the foundational model, then build on top of that. GPT was published may 2020. GPT 3.5 ("text-davinci-003" and "code-davinci-002") shipped a year ago, and ChatGPT was just a fine tuned on top of those. So they've had plenty of time to increase the training set, improve the architecture and run GPUs full power to get a GPT-4.