Probably not important. However, if you were to discuss it with him you might suggest that it is not polite behavior. But don't make a big fuss.
It probably is experimental behavior. I am curious how you found out about this? If your son volunteered the info, or if you found out via the school or another parent?
It might be nothing more than experimental behavior. However, it wouldn't be a bad idea to have a mental health professional evaluate him. The school counselor may be able to assist with this. If it is more than experimental behavior, it could be discovered by a mental health professional. It is best to get this issue addressed while your child is young to prevent potential issues from developing later.