the listing itself is somewhat confusing, maybe because i am not into mp5's. doesnt sound like he is trying to mislead anyone.
is your beef with him the title? if so, big deal numerous auctions and for sale items list names of things that they arent. it gets people to look.
i really dont see a problem with it.
when i had a 300-221 for sale, i had whisper in the title. someone like you told me to take the listing down because it was not built by jd jones.