to be fair to the original poster of that comment, if you are already pointing earthwards and you have no functioning pitch trim and no elevator authority, then the existence of the roller-coaster technique is indeed academic.
But the crew
did have elevator authority. There was nothing wrong with the elevator. In each case the crew failed to de-select the stab trim cut-out switches as soon as it was evident an uncommanded unusual nose down change was occurring.
If they had promptly turned off the electrics to the stabiliser as the first action, the mis-trim would not have so bad as it eventually came. Once the nose was allowed to drop well below the horizon before pilot intervention, the airspeed rapidly increased making it difficult for even the combined efforts of both pilots (assuming they were coordinated in the first place) to fall back on the roller coaster method to regain pitch authority.
It was probable that neither of the two crews were aware of the roller coaster method of recovery to trimmed flight. I am aware of at least one operator who practices the roller coaster in the simulator. The simulator instructor places the simulator into a dive to simulate a runaway stab trim. He then instructs the crew to heave back on the control column to the horizon only and then relax the elevator back pressure and attempt to operate the manual trim backwards during the momentary unloading process. By then the aircraft has increased speed so quickly that it becomes almost impossible to pull the nose as high as possible above the horizon to commence the roller coaster.
In other words the instructor is at fault for setting up the scenario badly in the first instance and giving the crew no hope of regaining control by manual stab trim operation.
The crew wonder WTF and go away to have their coffee without having learned a thing. Of course there are limits to the successful operation of the manual stabilizer recovery to trimmed flight. But if the simulator instructors don't have a clue then no wonder the flight crew can be caught out