No, it's not. In fact, they learn VERY quickly! They also learn what gets them the most attention. So, if you have a mouth that's, well, something similar to a sailor's, then they'll pick it up fast and then embarrass the heck out of you repeatedly, since you'll probably tell it "no" or make a big a fuss when it says something unpleasant.
Repetition is all it takes for a bird to learn a word, which to them is just like another bird sound, and Greys don't take long to learn a word at all!