As I said, it's all about how locked out on Coil work.
Say you didn't get to do Coil after reset, you are fresh. You queued DF, you get into turn 5, now you are stuck at turn 5 and CAN NOT go back to less than Turn 5. Woo hoo, you just forfeit your chance to farm a lot of once a week iLvl 90.
If you want DF you will have to separate EACH objective of EACH turn into a separate queue.