I have made a similar observation, maybe even stronger: In Lower Austria, I speak the dialect, but only 50km away in Vienna, people speak in more of a "standard German" way, I'm guessing due to the large influx of German migrants and because the dialect is considered lower-class (by the younger generations especially, who, probably due to social media, speak very Germany-esque) and I've noticed I myself also switch to a "standard German" type dialect.