That is the demonstration as described by Roscoe, but I do not think the physics requires the steady state to cause the illusion.
Syd, as I understand it the steady state is required because the semi-circular canals stop sensing movement because there is no acceleration in any plane to create the sense of movement - when the head is suddenly moved there is acceleration and hence the confusing sensations in the balance organs.
Whatever the cause it is unlikely to be new, but how prepared are helicopter pilots these days, to cope with the somatogyral illusions?
British Army pilots are required to undergo disorientation training in the air on an annual basis.
Brit Mil pilots all go through similar training at RAF Henlow.