[Gameplay (probably)] One For All Instant Bans Bypass Glitch (Karthus)

While playing with 4 other friends (a 5 man queue) we decided to have some fun and have all members abstain. The first time we did this, Rengar was chosen, and we had some fun being weird and building AP, AD, and tank, but that's not the issue. The next game, we abstained again, and this time, the game decided to give us Karthus. Karthus is an instant banned champion. And we could actually play him. We had a very long game against a Darius, eventually winning, but from Champion Select, we decided to report this right away. Basically steps to recreate:

1. Have all 5 members of the team abstain from selecting a champion.
2. Hope you get Karthus.
3. Have a terribly sad game of building AP/Magic Pen and ulting.

(The match history isn't working for me right now so I can't send the link. I do have a Baron Repays file as well, but I don't really know how to send/use that either.)