I don't think this is true, they would have stated that its being handed off to ChatGPT in those cases. My first thought was that this looks like Grammarly. This isn't new tech, it's possible Apple developed it in-house or it comes from one of the AI startups they've purchased over the years. While it wasn't mind-blowing, examples like these that seemed to come from within the company were hopeful hints that they're taking the catch-up game seriously, same with the Private Cloud powered by Apple Silicon servers.