Can an all wheat flour be high in protein, yet low in gluten?
I can't say that this is the answer with 100% definitiveness, but I do have a theory that seems valid. Usually, flours are milled and ground with the endosperm, which contains most of the starch and protein. The germ contains proteins, fats, and vitamins and the bran is primarily fiber. The fats, vitamins, and fibers at a molecular level would contribute some interference to gluten formation.

In addition, whole wheat flours cannot be ground as finely as endosperm-only flours. Because the size of the flour granules/clusters are larger in whole wheat flours, the proteins within the flour granules are shielded from added water. This means that less flour proteins come into contact with water, which means less gluten formation.