Initial flight control rigging according manuals will give you a more or less desired RPM with a full down collective (power off). some finetuning is required after this initial set-up. This is done to test fly straight auto's; depending on manufacturer, graphs correcting for weight, temp and DA will lead to a certain desired RPM region. (done it lots of times, and almost all of them needed additional adjustments to get it right.)
Ofcourse a real one never occurs with the conditions (Weight , temp etc) at which the final rigging was made.
However the whole idea is that when adjustments according the manuals are made, that RPM control is possible under all conditions.
Ofcourse it's easier to correct for over RRPM's (pull the lever a bit) than for under RRPM (manouvering) During the first seconds of a power off situation the first thing is to bottom the collective and at the same time minimizing the pilots effort to control RRPM. (minimize the already sky-high workload)
So I think there is such a thing as a wrongly set auto RPM.
cheers YB