The full Akamai report linked from the article also outlines that this technique (accessing UPnP from the Internet while pretending to come from the LAN) allows

The full Akamai report linked from the article also outlines that this technique (accessing UPnP from the Internet while pretending to come from the LAN) allows to expose the router's LAN services (e.g. web interface) on the Internet. I wouldn't be surprised if it could be also used to scan your LAN and to connect to any local machines, to access unauthenticated resources and to brute-force your passwords.