The reason BA have put so much mouth music into this is because it is your last chance to trap the threat of flying a beautiful 3 degree non precision descent into the undershoot with the wrong qnh set. EGPWS will not save you for a 10hPa error. Agree it can be overkill on a glide path, but is still useful for SA. Most CFIT occurrences I read about seem to involve crews that thought they were in the slot. I quite like the 'if we get it beyond 9Dme or above 3000 ft, we've made a mistake, or we're not where we thought we would be" approach.