Cleaning up, powering up, repairing. Those are just other words for refreshing. A healthy person can distinguish between refreshing and unrefreshing sleep, and so can a sick one.
It has a whole litany of particular qualities. Its also associated with other neurological reactions which our bodies do not produce in a normal manner. Examples: yawning and stretching.
So I am confident they will figure it out someday. What is so odd about our sleep problem.