It’s the same rules as when someone over-estimates your fluency in another language. When I was first learning Spanish, I asked people to slow down all the time because I couldn’t keep up. It seems most people are good at honoring that - at first. But at a certain point, they go back to their normal speed (or volume.) So I had to either constantly ask people to slow down, or just smile and nod through clumps of words that sped by in a blur and hope I interpreted the speaker’s tone correctly.