Trim Runaways
It would appear Boeing's stance is that the MCAS events are basically Trim Runaways, something that is trained regularly. So, there's a very simple question here: how many 737 trim runaways have been successfully handled over the decades? If the answer is 'lots' then there's strength to their argument. Conversely, if there have actually been very few trim runaways, two catastrophic, one may wish to question whether the event is routinely manageable despite what happens in the sims.