The 61 is different in that the servos are not dual, there are two in series, one a smaller aux servo, and one the big primary. Most newer helos have a dual primary servo, with identical tandem cylinders and dual pilot valves. These newer servos really cant hardover, since a single failure will cause one to try and move but be restrained by the other. Presumably a dual simultaneous pilot valve failure is too rare to worry about.
All this being said, the hand on the collective of a 61 will do nothing to stop the hardover, except to reach for the hydraulic shutoff switch quicker. Even so, turning off one or the other servo is a crap shoot.
I do not know of a hardover in a 61 servo, and would not think it worth losing any sleep over.