I thought that most of us had agreed over this one but the trigger for the runaway trim NNC was “continuous uncommanded movement”. For those who haven’t flown the 737, the trim moves quite a lot in bursts in normal operation, without a command from the pilots, as it is driven by STS, MCAS on the MAX and the autopilot. How could you tell that the trim moving then stopping was a) normal operation or b) a dangerous system failure? Answer: you couldn’t, without (secret) prior knowledge and continued observation. If you disconnect the trim every time it moved under its own accord you might as well pull the circuit breaker on the ground. It’s many years since I flew one but I still remember the “clunk clunk clunk” which was the most common sound on the flight deck.
It was asking too much of pilots dealing with a complex failure plus tactile and aural alerts, during a critical phase of flight where the trim was actually responding to their inputs, to immediately diagnose a failure of a system that wasn’t even documented and work out what to do. We now know that the sim trials were unrepresentative due to prior coaching.