Finishing the game opens the "unlocks" option in the main menu. It looks like this.
It shows you a list of challenges you can try to complete in new save. Doing so unlocks something new, like an outfit, strong weapons or cheats. One of these challenges is to kill 200 abominations. You have only a year to do that (All challenges can be completed only in the first year.) and it takes quite some time to do so and because of that bug, all that time he spent killing them was for nothing. That's why I want to add that temporary cheat, so he can finish the challenge without having to that all over again in the new version.