I think it's kind of unclear. They don't understand the mechanism and I don't think there are more than a handful of studies on this topic.

With the drop in A1C, maybe some of those subjects created a hypoglycemic situation and that impaired blood and oxygen transport to their nerves, thus increasing the pain. Or perhaps, the drop in A1C was causing their nerves to repair, also causing pain. Interesting stuff. Thanks for sharing!