This is an important finding, not because it confirms something that seems obvious for many people (ie. prolonged sleep deprivation = worse performance), but because it can help change the dominant management style in companies. Overworking is a very old problem, but hopefully similar findings will boost the strength of counter arguments.
Although I agree management styles should change based on studies like this, I'm not optimistic they will (at least not very quickly). Evidence against the efficacy of long work weeks has been around for quite a while[0], but that doesn't seem to stop most managers from expecting employees to work more hours.
