Can any qualified, professional pilot explain how the described flight profile could be termed a 'normal descent' and to give his/her opinion of the competence and mental state of the pilot executing such a descent?
I can pretty much guarantee that the above quoted flight profile didn’t happen. FlightAware doesn’t produce reliable data all of the time and ATC would be on your case within seconds if you started climbing back up having descended, especially in a busy TMA.
BA, like many airlines, runs a FOQA program. All the data from that flight will have been processed and any exceedances or odd behaviour flagged up for closer inspection. This is then tied in with pilot reports (ASR, MOR, etc.) to give an overview of any event(s) and whether anything needs to be done. As an example, some years ago they were getting a lot of high ‘g’ events at Madrid and it turned out to be the runway surface profile that was causing them.