Vanguard doesn't terminate a game with a cheater, yet instantly bans the account as soon as the game ends.

Pretty much the title. We played a game; there was a fresh level 30 botted account playing Xerath with outrageous scripts. We used the in-game feature to report the player and agreed to surrender early. No big deal.

As soon as we passed the honor screen, my duo and I saw the feedback report pop up saying that a player we played with had been banned for scripting. The account hasn't played any more games. My question is, if Vanguard detected that the player was cheating instantly, why wasn't the game terminated? How does that even work?