The most important part is the phrase:-
’In the event of an uncommanded horizontal stabilizer trim movement, combined with…’
which rests on the assumption that movement is perceived, in combination with…
From what what has been deduced so far, the crew of preceding Lion flight did perceived unusual trim activity, but did not directly associate the combination as described in the AD (MACS was unknown at that time). Fortuitously an association with ongoing Air Data alerts and indications, and perhaps previous maintenance action linking with the known STS, the crew chose to inhibit the trim.
The supposition in the accident is the crew did not associate the Air Data indications with trim, perhaps biased by the situation before flap retraction where the indications were of unreliable airspeed. etc.
Therefore without appropriate perception and the linked association, the situation may not be fully understood and thus the electric trim not inhibited - residual risk.
The defence / mitigation of this depends on operators disseminating the AD knowledge so that crews might be aware of both the failure mode of MACS and the risk of misidentifying the situation.
Our safety remains, as ever in the ability of the pilots, on the day, in the situations they perceive.
CONSO ‘why the AoA option’ … , - more associated with the optional AoA display on EFIS
What value would this alert contribute to a MACS situation; ‘a good idea’, or ‘it will help confirm the situation which can be deduced from several other features’.
Alternatively it could be a further distraction in a situation which might be overly biased towards AirData (especially flap down), and a continuing, mind sapping, situation biasing stick shaker.