Yes I think they may be using fluffy bunnies, but this is not always the case. Today I had a member of my clan getting 0% because he did not read the message and has quit the attack like usual in the first 30 seconds (yes I told him he is dumb for not reading it).
Snivel, thankfully the new update specifically prevents the activity you speak of! 0% attacks help out your clan! Once a person clicks "attack" in a clan war, there is no turning back!