I wouldn't consider the jump from 382 to 386 words per minute to be "way faster". That said, in a periphrastic language like English, those 382 words convey less meaning.
Typically the same article originally written in Japanese is read in about 60% of the time than the translated version is read by a native speaker.
It's probably not so much when the original is not Japanese written by a native-level speaker, because the semantic density is usually lower.
Measuring word count would give you a completely different idea. It must also be noted that you don't usually read every single word in Asian languages since often whole sentences are short enough to recognise their whole shape. This happens in all languages but in ideograph based ones sentences take a lot less space in readable form (although they may take about as much if not more pen strokes).
It's probably not so much when the original is not Japanese written by a native-level speaker, because the semantic density is usually lower.
Measuring word count would give you a completely different idea. It must also be noted that you don't usually read every single word in Asian languages since often whole sentences are short enough to recognise their whole shape. This happens in all languages but in ideograph based ones sentences take a lot less space in readable form (although they may take about as much if not more pen strokes).