I can see Kent's point on the onus being on the resounding yes group to prove their point.
Let me see if I can help make things clearer.
IMHO, I think the people to ask would be the people with lets say at least 5 years of teaching experience, and 15 years of training in Aikido. What do they think.
Not taking anything from people with less experience, but, I think a teacher would be the only one qualified to answer this question.
Otherwise, its just bantering back and forth.
To defend my answer of "yes". I could easily say....If being an instructor isn't necessary to be a highly accomplished Aikidoka....Then why are all the highly accomplished Aikidoka instructors?