It is also possible he is being a guy who knows exactly what he is talking about and has the qualifications and experience to back it up.

If an aircraft starts pitching down, and it wasn't commanded by the pilot, and resetting the trim (temporarily) fixes the problem, the issue is almost certainly with the trim. If it is MCAS and a malfunctioning sensor or a failing motor that occasionally kicks on and drives the trim to its limits, the pilot response should be the same. This is what I hear Walter saying, and it makes sense. MCAS just makes it more probable to manifest.

The thing is the checklist says in a runaway stabilizer scenario, it will trim continously, but MCAS does not apply trim continously. Therefore it does not exhibit itself as a "normal" trim runaway. Checklist: https://i.imgur.com/K7El4K4.jpg

Hence, they might not have thought it was a trim runaway.

Not every emergency manifests as a textbook case. It isn't too farfetched to imagine an intermittent short running the trim motor on an intermittent basis rather than continuously. I'd still shut off the trim motor as a possible remedy, but I'm not an airliner pilot, just a guy who flys for $100 hamburgers.

I'd really like to see the NTSB report on this when it is released. I've read some of them, they're far more detailed and contain a lot of pertinent facts that were omitted from the usual clickbait sensationalist journalism.

If you did, I certainly don't see it in your arguments.

I think you should read his comment again, and evaluate tenses.