A helicopter can land with the engine out by using it's rotors like a wing essentially. If these rotors are fixed, then essentially it becomes a falling brick.
On the Volocopter, the 18 rotors are fixed pitch, but yeah, a couple of engine/rotor failures are no big deal. Beyond that, ballistic rescue parachute: autorotation is not an option.
I suspect that there can be a way to relatively passively control auto-rotation of drone-style rotors. Pitch control is much trickier. It's not unheard of (even model planes sometimes have variable-pitch propellers), but it would noticeably complicate the rotor, lowering its reliability. I suspect that a fixed-pitch rotor with an independent mechanical axis brake could be much more reliable with comparable efficiency.
It's like a wing in the sense that it resembles the operation of an autogyro, which has an unpowered rotary wing.