Francis, I believe your rifle with the round bolt handle may very well have started its life as an action bound for a military rifle. H&H probably was just buying actions and taking what they could get. That is all guess work on my part. Or the original buyer, as you suggested, wanted the round bolt handle. Only past history knows and we may never know.
There is one thing you could do to maybe help this investigation is to take a picture of the top of the front receiver ring so we can see what is stamped there.