Doesn't a technique like selfish mining (http://arxiv.org/abs/1311.0243 http://arxiv.org/abs/1311.0243) mean that you can undo past transactions faster than 2%

Doesn't a technique like selfish mining (http://arxiv.org/abs/1311.0243 http://arxiv.org/abs/1311.0243) mean that you can undo past transactions faster than 2% of the time, though?