I don't know this expression but I partially agree with it. 

Polish language is more difficult for understanding in the same way as French because of complicated pronunciation and many unique sounds.  

But for me as Ukrainian it is more easy to understand Polish that Bulgarian for example, even though the diagram shows the same distance. And even though Bulgarians write in Cyrillic as we do, I can hardy understand a word, while I can easily catch simple information from the Polish text written in Latin letters.