As a Korean learner I think the article makes one believe it's the different meanings of words that cause problems, when it's more the fundamental difference in how the language is spoken in every day situations.

E.g. see the other comment by the Korean speaker here:

> Vocabulary changes depending on context, relationship, social distance, age, and whether the situation is public or private. North Korean speech is often more direct [...].

Also Korean slang changes incredibly fast.