It is not about ethnicity. Central Europe is a diverse place. In a continuum rather than hard borders. Especially as Austria was multiethnical state for several centuries. Generally there is a lot of similarities with southern Germany, but not more than with Czech Republic and va lot less with Germans from the North.

Austria had been an independent country for a long time, different traditions, different customs etc. I don't understand those you people on the internet who inist on denying Austria's independence. Are you doing the same with the Netherlands and Germany? With Denmark and Norway? Lebanon and Syria? Ireland and England? This obsession is cringy.