Why the apparent lack of monitoring of the vertical profile ...?
Perhaps this is a symptom of reducing exposure to NPAs because of the availability of 'precision like approaches', which is related to automation dependency - the skills of monitoring are degrading.
Extracts of a study into "Loss of manual flying skills" suggest that this is due to the lack of recency in monitoring the flight path and increased mental workload, irrespective of automatic or manual flight.
In addition, modern aircraft offer the crew more technical options and facilities, e.g. FPA, which require thought about which one, and when to use them, including hazards they might generate.
A dominant mantra of the ALAR Tool Kit was to monitor altitude against distance - altitude first because that's the life saver. Yet with the availability of advanced displays and navigation features, simple cross checks may be overlooked or never be part of flying awareness (weak training).
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The majority of the cognitive demands were associated with the vertical profile and energy management aspects of the approach task rather than the lateral aspect, suggesting that the former is a more cognitively complex activity.
... the vertical profile and aircraft energy is heavily dependent on mental computation and can demand significant working and long term memory capacity if an efficient model, simplified through heuristics (rules of thumb)
, is not available."
Continued learning (professionalism) may also feature; lack of exposure, fewer opportunities to learn / refresh knowledge, and even a complacency of not requiring to learn because the automatics will provide the answer.
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... at under certain conditions pilots are slower to acquire this knowledge structure, or perhaps learning simply fails to occur at all."
Note that this is not about auto / manual flight skills, it is the willingness and ability to employ mental skills associated with forming and retaining a good mental model, planning ahead, and knowing what systems to use, when and why - which are the important parameters to monitor.
The study concludes -
"
Subjective data and anecdotal evidence suggested that pilots of highly automated airliners may be vulnerable to the loss of their manual flying skills. However, there was insufficient objective data to support this safety concern and guide any remedial action. ...
The cognitive task analysis study revealed the dominant role of cognition (mental activity)
in manual flying skill. Expert pilots reported using highly refined mental model structures and heuristics (rules of thumb)
in order to predict the performance of their aircraft in its dynamic environment. The study found that the level of refinement of these models is closely linked to the performance achieved in manual flight. Pilots reported using advanced meta information gathering meta-cognitive (the method of our thinking)
skills to isolate elements of the control problem, reducing its complexity, and narrow their information scan and reducing cognitive workload . ... expertise was closely linked to mental model structure. "
Where operators allow more manual flight practice, then the tasks must also be mentally challenging.
The Loss of Manual Flying Skills in Pilots of Highly Automated Airliners