[jlpom]

> Alternatively, perhaps elevated orexin levels during the day cause wakefulness such that you just don't need as much sleep, regardless of how efficient the sleep is.

As noted elsewhere ITT, there is a strong biological need for sleep, and its main role is very likely to reduce reactive oxygen species (though the amount needed vary by genetics) Orexin levels increase the noradrenaline ones, which is one of the few antioxidants able to reach neurons (along with melatonin) and by this way also increase slow wave sleep, making it more efficient. So yes, this could be a way they would need less sleep.