I had a look through this and I didn't get the main idea. I understood that it you take a grammatical sentence in Swiss German and swap the accusative and dativ

I had a look through this and I didn't get the main idea. I understood that it you take a grammatical sentence in Swiss German and swap the accusative and dative cases around for one or more nouns, you get an ungrammatical sentence. I don't speak a language with cased nouns so maybe I'm missing something, but I didn't find this surprising. Wouldn't this be true also in German for example? Then this feature of Swiss German seems to be related to the 'context-freeness' of the language. I couldn't understand what this property was from the article, or from the (very technical) Wikipedia page [1]. Can someone give a less technical explanation of context-freeness? [1] https://en.m.wikipedia.org/wiki/Context-free_grammar https://en.m.wikipedia.org/wiki/Context-free_grammar