Perhaps SI affects some pilots and not others? I recall my first night takeoff in the P51 Mustang. At the time I only had 240 hours total time. Now that aircraft really accelerated on take off. I glued my eyes on the artificial horizon and directional gyro once airborne. I certainly don't recall any problems during the initial and subsequent climb which according to my log book was to 15,000 ft.
I have experienced "the leans" in many aircraft but never SI and that includes flying jet transports for decades. I suppose the question needed to be answered if some pilots are more prone to SI than others, could that be proven medically? if so, should they be denied a pilot licence or perhaps restricted to day VMC flying only?