In what sense are we sure that natural language actually contains these long-term dependencies (i.e. k > 25) in such abundance that they would show up in datase

In what sense are we sure that natural language actually contains these long-term dependencies (i.e. k > 25) in such abundance that they would show up in datasets of current size? When I was younger, I took Latin, and while some of the sentences definitely demanded a fairly large attention window, I'm not sure such long dependencies would show up often. Even then, I wonder how many humans alive would correctly pick up on an incorrectly translated word in a text by Livius or Caesar even - maybe this is different for modern languages but I feel they tend to use shorter sentences. Dependencies that transcend a single sentence are less common, maybe even so uncommon that a model will not pick them up during training. Can someome with experience in the field comment?