b. your body moved with respect to the wing, which was rigidly attached to the inceptor
Thinking back to when I learned to fly flexwings this I recall was the single biggest point I had trouble with. In anything else, you take your visual horizon references relative to the aircraft (instrument panel, pilots eye position, etc.) whilst in a flexwing you take your external references relative to the control - in practice the basebar.
Considering the number of things I've flown since, it's perhaps surprising that this fundamental difference hasn't subsequently given me trouble. My best explanation for this is that the environment becomes totally different and my "learned response" when presented with a flexwing seat, panel and basebar acts consistently in a particular manner - whilst if strapped in with a stick in front of me and a high instrument panel I'm "conditioned" to behave in another.
G