It kind of goes along with the thought in the Greek Scriptures about the anointed being "ambassadors substituting for Christ." While that applies only to the anointed, the WT will refer to members of the great crowd as "envoys." Seems like it is splitting hairs to me.
I have always been taught that while we who were of hte great crowd were not in that special covenant relationship with Jehovah, we, by means of our actions, were his witnesses. I believe Odrade is right. She is very witness sounding. great lingo.