PurityPaulOR said:

If two explanations both fit, the useful question is which one predicts something the other does not.

I am going to disagree with the direction of travel here. The thread has converged on the tidiest answer rather than the best-supported one, and those are not the same thing.

One concrete data point for the thread. Say what you would expect to see if you were wrong, before you look. It is a small discipline and it changes what you notice.

Ask again with the specifics and you will get a better answer than this one.

NeuroNate said:

I am going to disagree with the direction of travel here.

There is a second half to this that has not been said yet. The useful move here is to separate what is established from what is widely repeated. Those two sets overlap less than the confident tone of most write-ups suggests, and the second set is where nearly all the disagreement on this board comes from.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

A narrower follow-up, since the general answer is now clear:

Was that from a primary source or from a summary of one?

Closing the loop on my own question.

Closing the loop. The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.