[MiguelHudnandez]

Legal concerns aside, aren't Youtube captions primarily AI-generated in the first place? I know some authors meticulously hand-craft their captions but that can't be the case for the vast majority of videos.

Therefore isn't training AI on this basically poisoning your own model? The caption quality is good but there are mistakes in pretty much every video I watch with captions.

[eigenvalue]

They are almost certainly extracting the audio and then using Whisper or other superior speech recognition models. I made a free tool which can do this very efficiently for whole playlists of YouTube videos, so I'm sure they can do the same:

https://github.com/Dicklesworthstone/bulk_transcribe_youtube...