Yes. Based on conversations I’ve had with OpenAI staff, Davinci started unexpectedly developing the ability to answer longer questions as they scaled up normal InstructGPT fine-tuning some time in the past year. They don’t take down old models when the default one updates so you can see the version history implicitly in the availability of old models.
It’s not that implausible. It’s trained on many examples of instructions followed by answers, and it’s meant to (and does) generalize to unseen instructions. After enough training, it also generalized to instructions of previously unseen length.
