@Riot: Why is the Leaverbuster active for co-op vs AI?

This is something that I was always kinda curious about. In bot games, when a player disconnects, one of the bots will return to the fountain and not leave unless the player team is attacking their Nexus. Bearing this in mind, there's very little disadvantage if a player disconnects during a bot game, yet you get punished anyways.

I know this because the first time I ever got the "you left a game in progress, say you won't do it again" window was from a bot game that I had to leave partway through because something came up in real life.

I was just curious why this is.