Having looked at the ADS-B Google Earth track in more detail I start to think the -200ft altitude value reported at the crash site can be an instrument error caused by the impact. The QNH at the time was 1027 which implies about 370 ft height difference to the track's readings which are referenced to QNH 1013. This is an excellent fit with the airplane's level-out altitude reported at 1625 ft, which applying the 370 ft correction fits exactly with the 2000 ft indicated on the approach
chart.
Still, for some reason, after the FAF, 6.2 miles out (EH621) the track shows that the airplane descended with up to 1300 fpm instead of the about 600-700 fpm indicated on the approach chart.
Another thought is that the crew apparently believed they had engine power available. Otherwise, if they had been aware of a total power loss, a natural option would have been to turn slightly left where there was a much larger and more open field and no roads increasing the hazards.
Well.. speculation... FDR will tell.