Pending other evidence being adduced, I'd suggest that an explanation fitting these few facts is a somatogravic illusion, the response to which sufficiently abrupt to place the aircraft into an unrecoverable attitude even if a recovery was attempted.
While I understand the medical side of so called somatogravic illusion, I cannot understand why a veritable stream of airliners are not crashing on take off after lift off (very marked acceleration) or from the thousands of IMC go-arounds that must take place in any one period throughout the world. In all cases one would think that the pilots would all be affected by the acceleration forces involved with speed increase after lift off or go-around.
Catapulting from an aircraft carrier at night or IMC would surely be the most dangerous risk from SI yet rarely do we hear of these aircraft crashing into the ocean after take off. Having flown early piston engine fighters (Mustang) as a young man with only 200 hours in my log book I don't ever recall experiencing SI at take off at night in that aircraft and in fact I have never experienced this phenomenon in my entire 60 year career as a pilot and that includes jet airliners.
If SI is as insidious and potentially dangerous as advertised in flight safety circles, it doesn't explain why thousands of pilots are apparently unaffected and therefore don't crash when faced with IMC take offs and go-arounds