Sounds like a basic fallacy in the definition of half discharged.
No, it’s just that storage capability and discharge rate are two completely different things.
I have electric R/C helicopters. At 4.2v/cell they take off like a rocket. At 3.8v they will sink to the ground (although I don’t usually let the batteries get that low). There is still energy stored but it can’t be discharged at a high enough rate to usefully turn the rotors (and would damage the batteries if you could).