I think people have varying opinions on this. Many of us don't really want to launch people into a phony conversation -- you convince the other person that you understand the language, then they talk for a while, and then they realize that you didn't understand anything they just said. Now your newfound friend thinks you like wasting their time.
This happens all the time in other contexts. "Have you seen movie X?" "mm yeah" "what did you think about the part where <20 minutes of explanation>" "oh you know I didn't actually see the movie I just didn't want to say no". The reason people do this is because they hate saying no, and 50% of the time having seen the movie / heard the song / know the celebrity / is not actually relevant to the anecdote. But when it is, you sure look like an idiot.
This happens all the time in other contexts. "Have you seen movie X?" "mm yeah" "what did you think about the part where <20 minutes of explanation>" "oh you know I didn't actually see the movie I just didn't want to say no". The reason people do this is because they hate saying no, and 50% of the time having seen the movie / heard the song / know the celebrity / is not actually relevant to the anecdote. But when it is, you sure look like an idiot.