I agree with Capn Bloggs. I fly an aircraft with EGPWS and all the other kit but there is a big warning in the front of the book saying, in effect, "don't use this for navigation". The look-ahead terrain function is a life-saver but its purpose is to encourage you to get the hell out of there, not to examine it at low level and thread your way around the peaks, such as they might exist in the database. If you had no other choice, e.g. a technical problem that left you below MSA in IMC despite all your efforts, then steering the aircraft using the terrain map might be the best option out of a bad lot...
If they took a low-level route up the side of the peak, I'd have thought the plain old GPWS would have being going mad as well with mode 2 & 4 warnings. It would be possible, if you were descending directly towards the crash site, not to trigger the warnings until very close due to the terrain underneath not getting in radio altimeter range until almost the last moment.