Youtube allows creation of auto-generated captions. What are they licensed as? Is it cc0 or can one use them outside the video or to provide a transcript to users after ADA compliance editing.
If these generated captions are mechanically created from (the audio track of) a video, then YouTube cannot claim any copyrights on those captions and therefor also not impose any copyright license terms.
This does not mean the captions are free of copyright, but their copyrights are fully owned by the copyright holders of the video (or possibly the copyright holders of the audio track).
Copyright law is intended to protect the human creativity that goes into creating something. As a purely mechanical transformation does not involve any human creativity (in doing the transformation), such transformations are generally excluded for copyright protection.