It's impolite. There is no such thing as waving goodbye. Waving goodbye is a casual and simple way to say goodbye. Regardless of details and so on. Of course, there is nothing wrong with this, and others will not care. I just suggest that you don't think so much. This farewell is born of simplicity and randomness.

In addition, I will tell you a sign language farewell way, which is very good and can be given to friends around you (cartoons come from the shape of sound)