Because normally without this drug we can go 0% (deep sleep) to 100% (full “on” mode, living life all the way)
They basically block us at 50%, this mean we cannot reach 0% that is essential to fall into a deep sleep, and we cannon reach 100% that is essential to feel an live 100%
If we can’t have a deep sleep we cannot recovery, because recovery happen 80% when we are into deep sleep, body and brain regenerate.
Since we cannot reach our deep sleep recovery is blocked, that time when we fall again into full 100% deep sleep then recovery start taking his place all the way.
I’m sure this is why we can’t recover early, because sleep, deep sleep, restorative sleep is the key but we cannot reach that kind of sleep.