Tourist, Prouty explains that an aircraft can achieve "windmill brake" conditions; i.e. the rotor is being driven by the upwards airflow and falls at a rate roughly equivalent to one where a parachute of similar diameter was fitted, rather than rotors (don't ask me to do the maths on that....). Therefore a state of VRS still exists in autorotation (if recovery actions aren't taken by then) and may be the final "symptom" of fully developed VRS.
He also states that there is evidence that a true vertical descent in fully developed VRS may result in a lower ROD than one at a 70 degree descent angle, i.e. one with some forward motion. It appears that as the aircraft is recovering, a transitory stage of a higher ROD may have to be passed through.