The thing is, when you become accustomed to the language there is no such thing as keeping stuff in the working memory. I think that’s just a convoluted way of explaining the processes that are behind speaking/understanding a language. As a native speaker of German I pretty much know at the first few words of the sentence which verb/words will have to follow and how the sentence will have to end. The meaning or information is not necessarily encoded in the verb or in those words that are moved to the end of the sentence. It’s just the shell of the sentence that is so common and you‘ll see/hear so often, you don‘t think about it anymore. Ultimately it‘s just pattern recognition that doesn’t require a lot of effort, IF you know the sentence structures that go with it.

That’s also why I guess learning a language with a lot of input goes a long way to absorb the structure of a language, because at some point you‘ve seen everything and only the important bits (the real information) remain if you look at a sentence.