" This is not just disorientation and it is not the leans, but a full-blown sensation of spinning about all three axes."
This sounds like what it can be like if you have ever been in a Barany chair which is a vertigo inducer training device. The chair spins smoothly while you wear a blindfold. Youn re told to put your head in various positions and asked to determine direction of spin etc. By far the most dramatic and frightening demo was where they had you lower your chin by your chest for a while as the instructor spins, stops spins in the other direction and eventually tells you to raise your head. The sensation is best described as feeling like you've been pitched from your pilot seat, out of the helicopter in a hover at altitude. It made me make noises I've never made before and grip the chair, although that made no difference. The instructor then pulled off my blindfold to allow the rest of the class to see my eyes, which were uncontrollably darting around for several long seconds before I almost fell out of the chair. It was so unnerving as to instantly change my perspective ( no pun intended) on spatial disorientation. You sort of think you know how to deal with it but after this demo I'm not sure I want to find out.