From what I have read they don't really defend it at all. They just say they have things that put them away from the game for more then 30 minutes. I think this is the people who just want to Q for a dungeon and walk away.
There is no real defense for this, so people are just going to say, "Well I AFK for longer then 30 minutes" This is a non issue. It will just stop people from abusing game mechanics, which from the fixes in this last patch it has become apparently clear, people believe in exploiting... SE you got your work cut out for you....