Mansfield, turning your ‘elephant’ around, consider the actual threat to safe flight. The aircraft was not flyable because of the trimmed condition; the abnormal trimmed state.
AoA failure in previous variant 737 other aircraft types can be managed. In the Max, MCAS with AoA contributed to the trimmed condition, but so too could other trim failures - continuous runaway (not this accident).
The Boeing argument is that the abnormal drill for trim runaway would mitigate the MCAS induced trimmed condition. The mounting evidence is that this is not so, particularly considering crew’s inability to understand the abnormal trim motion - the initial MCAS trim movement was exactly as designed; and thereafter the physical impossibility to move the trim wheel manually.
The obverse is if the trim runaway drill will mitigate a ‘trim runaway’, (no MCAS or AoA involvement), particular with larger trim offsets and / or higher air speeds; does the MAX differ from the NG in this respect.
There are differences between the two trim failure initiators, but each depend on human perception, understanding the situation, choice of action, and acting - which may or may not work.
Managing the abnormal trim state depends on an assumed human ability; that the crew will be able to identify and mitigate the threat.
Thus the fundamental question is if reliance on human ability in this instance has been stretched too far; highly questionable for mental workload and situation assessment (+ no training, no published system description), even more so for the impracticality of crew procedures( + none / hastily issued inadequate drill).
‘It is very difficult to change the human behaviour, but you can change the conditions in which the human works’ - James Reason.
In changing the conditions of work, Boeing must consider all possible contributions to the real threat - all trim malfunctions, all abnormal trimmed states.