As someone who's been diagnosed with hypersomnia after several doctor's visits and sleep studies: that's correct. The fog very rarely goes away.

There's the occasional good day that comes once every few weeks/months to remind you of just how bad things are, but otherwise it's just constant fog.

Similarly to depression, things like a good diet, regular exercise, a regular sleep schedule, a bright light as an alarm clock all help improve things somewhat. Ritalin also helps if your heart can handle it.

I wasn't trying to suggest that regular sleep deprivation is as bad as what the article describes. The language and scare quotes made it sound like they were explaining "sleep fog" as a new concept.