Yes, if there was something interesting there you'd think since 2017 something would happen. Reinforcement Learning (that is compared with) is not particularly famous for its performance (it is it's biggest issue and reason for not being used that much). Also transformers don't use it at all.
OpenAI has turned for profit and stopped releasing any tehcnical details regarding architectures or training. So how do you know that nothing has happened? Because they didn't release it? Do you see the issue here?
But given that they don't seem to have worked on it since, I guess it wasn't too successful. But maybe there is a way