Language used in the 2021 film

I was rewatching the film recently and again I was impressed by the use of language. In the training scene with Gurney, there was a direct quote from the book - "you're not in the mood for fighting? Wtf?" (Paraphrase). Most of the film also used Dune language. But I felt that when Paul and Jessica were alone in the desert, they stopped speaking "Dunish" and started speaking English. Did anyone else notice this / feel this way too?