BOAC, in principle, (as I understand PANS OPS) the terrain / obstacle clearances for NPAs are divided into three segments; IAF - IF, IF – FAF, and FAF – MAP. These segments have clearances of 1000ft, 500ft, and 250ft respectively. Thus, your assumption would be correct (but still bad practice). However, the chart shown in the ASTB report shows two ‘minimum’ altitudes after ‘F’ (6 DME), 1250ft and the MDA of 1140ft. If ‘F’ is the FAF as indicated by the chart, then there is some ambiguity between PANS OPS and the chart being used (another chart hazard?). It would appear more logical that the FAF was at ‘ROC’ (4.2 DME) beyond which MDA applies. Perhaps someone with access to the originating Australian procedure chart could comment.
Re ‘can / should’ be a climb. The history of the certification wording for EGPWS will show a valid, but exceptional, reason why a turn vs climb maneuver is allowed at the amber level. However, the industry’s experience and continued improvements to the EGPWS alerting algorithms might now show that a climb is always a suitable maneuver, hence IMHO, the same simple procedure for an alert and warning – pull up, can be taught and practiced. This also avoids any crew deliberation on what to do after and amber alert, perhaps minimizing the risk of debating the reason for the alert – it doesn’t matter, the aircraft should not be where it is. Furthermore, if a turn was to be flown, it implies the use of the terrain map, which may not be as accurate as the basic navigation aid (including ADF in remote areas) unless the EGPWS uses an internal GPS receiver – i.e. beware map shift (we get complacent when using high quality technology in areas well equipped with navigation aids).
I think that the industry is too harsh in attributing connotations of blame on the crew, i.e. ‘mishandled the situation’, etc. Lets see what the investigation discovers; several issues have already been identified that can lead to an error, and the use of VS might have been a simple mistake, or slip (cf Strasbourg). This is not to excuse the crew / operator; a professional operation should have detected one or more the errors (and briefed the hazards). Crews are accountable for a safe operation (before the event) and on the evidence so far this operation appears not to have achieved the required level of safety, but we only believe that due to ‘an error’ (identifiable after the event).
Edit; I note that there are procedure differences between PANS OPS and TERPS. TERPS uses 250 ft, whereas PANS OPS minimum are 295 ft without a FAF and 246 ft with a FAF. This might answer the ambiguity in minimum altitudes before / after ‘ROC’, but it is still not clear to me where the FAF is.