One small comment, it definitely is not essential:
I have always learned wrist grabs as preliminary for other attacks like strikes and kicks.
I was often taught this attack is a traditional one, based on preventing/delaying you from drawing your own weapons. Similarly to Suwari-Waza, it also has significant role in the learning process, provided one is aware of the existence of other attack types and utilizes the learning from this type of attacks to take advantage of those issues.
The spirit of this discussion made me uncomfortable. The Aikidoka seems too sure of himself for this to be any real investigation\examination of ideas.