In this event, the Captain's (PF's) alertness was degraded by fatigue and a minor medical condition. Both pilots were very experienced (20,000hrs and 10,000 hrs).    

After briefing for an instrument approach but also with the possibility of the track being shortened, crew accepted an ATC offered shortened track. Subsequently ATC asked the crew to report when visual.

In the course of the approach the Captain selected inappropriate autopilot modes which resulted in the aircraft getting significantly below the proper profile. The Captain was misled into thinking that the aircraft was high by a spurious ILS glideslope signal caused by being outside the ILS coverage area. He relied on this as his primary vertical guidance as it fitted his mental picture that the aircraft was high although it was contradicted by other information. 

The First Officer was monitoring the instruments but detected from the visual scene that the aircraft was in fact low and advised the Captain of this shortly before the EGPWS alert triggered a recovery.    

The report noted that "the crew did not have a shared mental model of how the approach would be flown" and that "the absence of a shared mental model increased the risk that the First Officer would not identify and respond appropriately to the Captain’s actions". It was also considered possible that "general limitations of human monitoring capability....may have influenced the First Officer’s performance".

This event also appears to have been partly triggered by both pilots using a similar conflicting mixture of external and instrument cues in their mental model, triggered by the natural desire to move to visual cues and report so to ATC.   

If the crew had been using a PicMA,

1) it is likely that the these two elements might have been kept separate, as the F/O would have been flying the shortened route solely by instruments.

2) Despite his fatigue and medical issue, the Captain would have been more likely to have corrected any erroneous mode selections by the F/O, while being free to attempt to make the visual judgments needed to complete the approach without simultaneously flying the aircraft. At this point, about 3 minutes before the GPWS alert, the crew could see the ground and runway but visibility was affected by sun glare and terrain shadowing due to mid-level scattered cloud.