It's strange that Netflix would do that. In Germany, they pioneered consistently offering original audio. (For instance, Amazon Prime Video was available earlier than Netflix here, and originally most of their catalogue was dubbed to German exclusively.) Plenty of services where you can rent this movie also offer it in English (OV): https://www.werstreamt.es/film/details/2097679/the-green-kni... So it may very well be some weird licensing deal where they only get to offer this specific film for streaming without a surcharge if they stick to dubbed audio.