Ng versus NF when at ground idle and flight idle

In a turbine helicopter with a power control lever for the turbines, when at ground idle the turbine should be around 65% rpm on the Nf and 100% on the Ng. At flight idle I should be at 100% for both.

Is this a true statement?

It’s not intuitive to me since the fuel flow to the gas turbine (Ng) I would think would slow both the Ng and Nf down to 65% at ground idle.
Trying to get my custom helicopter engine in P3D to behave as real as possible. Which means I’m writing my own engine code for the gauges.

Is it also a true statement that when both turbines are at Nf of 65% the rotor RPM drops to 65%?

Here is a follow up after hours of research.

N1 and N2 turbines are not modeled at all correctly in P3D. Both are ALWAYS at 100%. That mis-led me. In reality, the N1 adjust with the power lever to be idle cutt-off, ground idle and or variable up to flight idle. The N2 turbine then follows the N1.

The remaining question I am still not sure of is - does the rotor follow the N2 precisely (in synch) since they are mechanically coupled, or does the rotor during startup lag behind N2 slightly because it has more mass than the N2 turbine. It seems they are linked one to one through the transmission at all times except when the turbine shuts down, then the rotor free-wheels and slows at its own rate.