Because of the steep angle of descent in a Constant Attitude autorotation, the ASI can have very large pressure/position errors, dependent on the position of the pitot and static.
In some helicopters including the R22, holding 20-30kt will almost certainly result in bent skids as the ASI over reads a lot and about 40 kt IAS is about the minimum. The same was true of the Bell 47 G4A, but not the G2 model which had differently a positioned static port.