The flight attendants at my Global 5000/6000 operator do use the forward lav for a rest area when the crew rest area is full of pilots on the 6000 and any time they need to sit down in flight with pax on the 5000. The jump seat is very inconvenient to operate and not particularly comfortable. Augmented flights on the Global aren't all that nice for any of the crew on a Global, but especially brutal on the FAs. I did 11.5 hours on one flight where the poor FA never had a chance to sit outside of takeoff and landing- the pax didn't sleep and had very elaborate meals.