Captions seem to have been updated sometime between 7 and 15 months ago. Here's a reddit post from 7 months ago noticing the update: https://www.reddit.com/r/youtube/comments/1kd9210/autocaptio...

and here's Jeff Geerling 15 months ago showing how to use Whisper to make dramatically better captions: https://www.youtube.com/watch?v=S1M9NOtusM8

I assume Google has finally put some of their multimodal LLM work to good use. Before that, they were embarrassingly bad.