Many pilots of piston-engine helicopters who are transitioning to a turbine become confused about how turbines operate. They expect to see a needle-split when snapping the "throttle" (really the fuel control lever) from Full to Idle and become concerned when they don't get one. But, depending on the type of aircraft and engine powering it, you do not always get a definite needle-split in a turbine. Helicopters powered by the RR-250 series don't always see a needle-split. At the Idle position, there is nothing controlling N2 rpm. The PT governor is out of the picture, and the N2 will be..."wherever." The N2 turbine is only "gas coupled" to the N1. Without a load on it, the N2 can be quite high even with the "throttle" at Idle. In a practice auto, if you're light and your NR auto-rpm is low at flat pitch, you might not see much of a split with the "throttle" at Idle. (Obviously, the N2 rpm can never be above the NR.) On the other hand, if you're heavy and the NR is high, then yeah, you might see more of a split. This behavior is puzzling for the new turbine pilot. Just remember that the throttle only controls the N1, not the N2.
Unlike piston engine ships, we typically don't do a check of the freewheeling unit operation with the engine running. We do that prior to starting the engine (by moving the main rotor blade), and we also do that when we shut down, where we would expect to see an N2/NR split.