Yes thats how slipper clutches work. There is no resistance to engine braking - ie if engine is spinning slower than wheels, it will just let the clutch "slip" so that it doesnt lock the back wheels up. Thats why its used in motorbikes as engine braking in bikes can easily lock the back wheel. Not really worth it in a car.
hmm my own experience on track on bike with slipper clutch is that it slowly engage the clutch with the engine; engine braking still occurs but the rear wheel doesn't lockup. I need to investigate this further
btw, tried a heal toe downshift earlier today... lol think I'll do it on closed road the next time...
This should help - http://en.wikipedia.org/wiki/Slipper_clutch
Standard on my bike. One less thing to orry about!