Whether you call all those others a "commentary" or not, there was a big difference in the tone and general contextual approach in the "James" (and also the Aid to Bible understanding, for that matter). The James commentary was written at a time when Ed wanted to approach a more "reasonable" application to the context of a verse. He felt that the society was becoming too dogmatic in just picking this verse or another by itself and then jumping to a wholly unrelated place in the NewTest. and chaining that in there. Remember, the popular books of that day were "Evolution", "Truth", and "Babylon the Great" -- topical subject books rather than commentary.
His philosophy was to let the bible writer James tell his story, and just make explanatory comments. The general watchtower disposition was to pick a favorite doctrine or chronology and then force context of various scriptures to tell their story. Ed was of course a "fader" in fact when he wrote this book - but I think he viewed himself as a sort of back-to-basics reformer at the time. As I remember the book, there was really nothing contraversial about it at all; except for the fact that it stuck strictly to the subject of James and did not go afield to prove other points.
Others who knew Ed in those days may differ, but I really think that he believed the society would eventually see reason and reform - right up to the very last when they booted him and his wife out on the street.
James,
p.s. - did we kind of get this thread off of what the CO says?