Client / server and P2P were not the focus of my point about FD choosing to use the UPnP protocol itself.
I think that was one of the reasons P2P was choosen. They still ended up with a game that can't run without servers and some bloated server code that they cannot release, so it probably won't work this way and when FDev goes out of business we will have to rely on the hacking community to revive their games, similar to what happened to Elite 2 and 3One day, in the dim and distant future, Frontier may close its own Elite servers. The P2P design may help any stalwarts set up their own Elite network somehow. So it's not necessarily all bad news.
Sorry, you've gone off on a wild tangent about "using" uPnP... as if something could "use" the uPnP mechanism for actual data transfer itself between the clients.
UPnP is used as the connection establishing protocol, in order to get Elite clients talking to each other via the matchmaking server. Elite gameplay packets themselves are UDP.