(with adjustable pitch propellers it can)
Well, a high aspect ratio rotor blade, with a weighted tip, which must turn at a few hundred RPM during auto rotation, and is exposed directly to "clean" oncoming air is one thing. A propeller which is not any of those things, and with a duct must have the air enter only as a result of a completely vertical descent, is very much another. I cannot imagine the autorotating propellers storing enough energy to arrest the high vertical decsent rate required to get them spinning.
I used to fly light hovercraft a lot. One of the safety elements of which you become rapidly aware, is that with any speed of consequence, and a travel direction other than "straight ahead", an engine failure is going to result in a rollover, and it is you who are being rolled over. For that reason, though it may not be immediately apparent, the structure of most hovercraft include something like rollover protection, if you manage to hang on.