Here is the question. Because I purposely constructed to be NOT opinion based, and cast it as "historiography."
I can understand why a question like "Could the Axis have gotten a negotiated peace in World War II?" be considered opinion based. But at that wasn't the question.
This question was, "has any other historical figure or historian (other than Churchill) commented on this subject?" Churchill was both, and I cited his commentary as an example of the type and level of evidence I was looking for.
For instance, an answer like "The U-Boat was Britain's greatest peril. It would have been wise for the Germans to stake all on it." would be an opinion. But "Winston Churchill said, "The U-Boat was Britain's greatest peril. It would have been wise for the Germans to stake all on it,'" is a fact, not an opinion. Churchill DID say/write this.
Put another way, this was a "meta" (data about data) question, not a "subject matter" question. Again, I can see why a "subject" question would be opinion based. But how can the presence (or absence) of commentary on a particular topic be other than factual?