Well there's two questions; first the question of whether the extractor works for average "Joe knucklehead" who doesn't prepare AT ALL and then there is the question of whether the extractor works for someone who's willing to crack the instructions ahead of time and has a bit of first aid training.

Kind of like discussing the success rates of armed self defense for someone that buys a firearm and one box of 20 cartridges (because that's all they're EVER going to need) and throws it in their sock drawer versus the success rates for people who prepare mentally, get competent instruction & practice regularly. The value of the conclusions drawn could vary dramatically based upon which group you plan to be part of.