Yeah, so of course a human speaking both languages fluently will be better. Still, when you use the large model the results are really good for an ai. The best I've seen so far. I don't speak Japanese so I can't vouch for the accuracy but the two movies I watched seemed to be translated well. Maybe it varies, or has difficulties with slang? I don't know.
Now if you want prefect subtitles you'll probably have to wait a few more years. If you want very decent subtitles however...