[Bêthberry]

I think it might be helpful to consider Tolkien's explanation in the Foreword to the Second Edition why he rejected allegory. It was to avoid a too limited vision of what the 'text' meant. He wanted readers to consider his themes from a larger perspective than just that of contemporary history/politics. When writing a different story or tale, he could well have decided that an allegorical style would better suit that new tale. But note that in the Foreword Tolkien rejects both allegorical and topical interpretations.

It is also very instructive to consider his comments on how his story would have gone had the "real war" (WWII) "inspired or directed the development of the legend". It is a very sobering indictment of the Allies in WWII.