Most creators on YouTube seem happy enough to just go with the automatic closed captions that YouTube generates during the processing of a video that takes place between the end of uploading and when it goes live for viewers.
But when reading from a script, it is much better to generate them from the script itself. The auto-generation is an assistive tool. I have asked him before why he doesn't do that, and he didn't give a coherent answer. He didn't know much about the feature until I discussed it with him.
I think the reason many creators "go along with it" is that they don't know about the feature and manually adding subtitles can take a lot of time (community submissions can address that), though if reading from a script, it could just be about copying and pasting.
Creating a translated version would count as a derivative work, so if you are going to do it make sure that you have permission from all copyright owners of content included in the original version.
He is the one who has the rights to it, and as far as I know, he will allow others to rerecord if they are happy to do so.