The bulletin refers to an already existent procedure.
Company Training: questions need to be answered
Company Maintenance: why was this gripe not fault isolated and fixed?
The description of how to deal with trim versus STS, and the need to turn off a particular system using the cut out switch looks like something that should have been practiced in the sim ... but how often?
From Boeing:
In the event an uncommanded nose down stabilizer trim is experienced on the 737-8 /-9, in conjunction with one or more of the above indications or effects, do the Runaway Stabilizer NNC ensuring that the STAB TRIM CUTOUT switches are set to CUTOUT and stay in the CUTOUT position for the remainder of the flight.
From this, I understand that one can turn it off. If one does not turn it off, one will be fighting it all the way to the next landing. (Do I understand that correctly?)