I have had a chunk of blade tape bubble and cause horrendous vibration until it finally came off - I have also had a whole blade pocket detach from the spar, again nasty vibration and lots of noise - both occurred about 2/3 of the way to the tip but scary as hell.
What levels of drag and vibration on a 2-blade system and a delamination at the tip would be, one can only surmise but that extra drag would have decreased the Nr even if he had kept the engine going - without it running, perhaps because he panicked and assumed he had an engine problem, he had no chance of retaining Nr.