The thread you linked reasonably concludes its "routed" P2P. In other words, P2P with, (1) a forced route through, and (2) a form of network address translation at, blizzard's server.
My speculation: this almost exclusively to protect the private IP of one client being exposed to another client. There is no server processing happening beyond connection verification to help mitigate desync attacks. Deliberate desyncs are still possible though, since I've been the victim of it.
My speculation: this almost exclusively to protect the private IP of one client being exposed to another client. There is no server processing happening beyond connection verification to help mitigate desync attacks. Deliberate desyncs are still possible though, since I've been the victim of it.