Let's think this through.
In steady state autorotation, total rotor lift = weight
A heavier aircraft therefore requires more lift in auto.
More lift requires more blade angle of attack or more rotational airspeed.
Since we have a max Nr in a real helicopter, the only reasonable way of getting more lift is to increase blade angle of attack.
In auto, however we encounter the problem that we can only increase the angle of attack by changing the blade angle with the collective through a reduced range compared to when powered as the arrow must still be positive to maintain autorotation.
That leaves us with ROD as a method of increasing the blade angle of attack.
ie, increase ROD to increase lift till they balance in steady state
Thus I reckon higher weight = higher ROD in auto.
The only occasions where I can think this might be altered is at very low weights where the drag of the gearboxes might dramatically effect the efficiency of the autorotation.
Aside from that I think the original premise is bollocks.