So the question then becomes, why is the game program no longer writable in the current generation? I'm guessing because random-WiFi matches use one of the two games as the "server" for these matches, rather than actual servers running them? They're worried about hacking? If that's the case, it would also explain why disconnects don't count as a loss for the disconnecter and a win for the opponent. Of course, Nintendo/GameFreak's extreme incompetence concerning online functionality could also explain that.