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