I’m rewatching Spirited Away with English subs I grabbed off opensubtitles.org and I had already been confused by some phantom lines that didn’t correspond to any spoken dialogue but this scene made it obvious what was happening- there’s extra lines added in places where the characters are facing away from the camera 
Either the subtitler was hallucinating or these originate from the dub. I grew up watching a VHS tape 
in Japanese with Finnish subtitles and I don’t recall this scene having dialogue
With Spirited Away, it’s important not to get dubtitles, which is what you did
I legit didn’t even know those were a thing! I mean yes, I’ve played games in English with the Japanese audio track and noticed some pretty large differences between the localised English script and the Japanese script but I didn’t realise anime dubs went as far as to add entirely new lines.
Lesson learned though, I went and grabbed another set of subs based on the Japanese version which made the experience of watching the movie far less distracting
It’s kind of a necessity. Japanese and English language structures are very different.
For example, you’ll typically hear names at the start of a sentence in Japanese, whereas in English, they can technically either be at either. Though, for the sake of engaging dialogue, are typically at the end of a sentence.
On top of that, most dubbed movies will try to sync lip flaps (turning away from the camera makes it convenient to utilise empty space).
And on top of that, there are quirks of language which make intonation more important then the script, for example “yes” can be inferred as enthusiastic or begrudging depending on the language, but makes more sense to translate is “Absolutely!” Or “If I have to…”, depending on context.