User blog comment:FairyRaven/Fairy Tail Chapter 368: The Third Seal, Review and Commentary/@comment-1153699-20140125173023/@comment-7418318-20140126103856

That depends. If he has something equally or even more important to do elsewhere or if setting the OS free involved making them believe they killed the one who held them captive for years and allowed Brain to twist them, it would make sense. Even though either case would carry the risk of a fallback once they learn the truth (if it woked in the first place).