I have no answers, only a couple questions:
First, does this mean the cranks also can't stay still while the wheel rotates? I assume so, since that would require the very same freewheel action that back-pedaling requires. So you'd have to pedal along with the wheels, like a fixed gear bicycle.
Second, how could it do that? I don't know anything about cassettes, but I assume they have the same internal pawl spring freewheel mechanism, and it seems to me something must be gravely boogered to make that fail.