Seems like they're walking back from the previous announcement, which said they'd give 12 hours of non-sleep time per day: https://news.ycombinator.com/item?id=9295874
There's a huge difference between 24 hours/day and 18 hours/day, but I don't think there's such a big difference going from 18->12, so I don't think many people will care about this improvement.