I know a few people who have worked there over the years and they confirmed the same thing - albeit with a huge caveat.
The two people I know said the 20% was a way for their brains to take a break and think creatively. Nothing was too crazy or far fetched not to try out. They said it helped combat the crazy hours and working from dusk till dawn. In short, it helped prevent burnout. I would be willing to bet the turnover rate will start increase as their employees start to work more hours, without any breaks, and nothing to give them something to look forward to and burnout starts to settle in much faster.
Sure, it's not going to make them go bankrupt, but it will have a real world cost to their bottom line.