Betteridge's law of headlines be damned, the answer is "yes". I've basically only used Duolingo for learning a particular new language. I started from nothing, and just did a little every day during the pandemic. Then I travelled to the country in question, and was able to tell stories in the language. Not easily, and with bad grammar and my vocabulary sucked, but this is more than being able to order at a restaurant…
I've seen this too, so many times. If I'm speaking to someone who has trouble with English, I can automatically speak slower, enunciate better, and use simpler words and shorter sentences. But some people cannot adapt the way they speak. I don't think it's because they are unaccommodating or impatient. For some puzzling reason, they just can't speaker slower and simpler. Ironically they might instead speak a bit faster as you observed, or louder.