Only reason I'm being pedantic here is because if the study was in-fact looking at parachutes from helicopters, it could actually be plausible that parachutes had no improvements when used with helicopters. Most, if not all pilots, don't wear parachutes because there's not enough time to jump out of a crashing helicopter to deploy one and the blades would probably hit you anyway (unlike a plane which you could glide for some time, helicopters are notoriously more likely to fall straight like a brick)
It is a normal procedure to be able to safely land this way when power has been lost, and in some ways is safer than a gliding fixed wing aircraft as you don't need a runway to land on.
Of course catastrophic failure is possible in a helicopter where the rotorblades can't turn, and then autorotation won't work. But then if a wing falls off a fixed-wing aircraft, they generally can't be controlled (interesting exceptions do exist like with the Israeli F15[1]).
[0] https://en.wikipedia.org/wiki/Autorotation
[1] https://en.wikipedia.org/wiki/1983_Negev_mid-air_collision