I think it's just very little fresnel. I usually avoid using those very dark maps, and do a tiny little overall reflection, to lessen calculation time.
Also, I think a lot of these so-called reflection maps are derived from the color maps by some software, and do not really represent what areas should have reflection (or bump/displacement). I refer to Pixplant for instance, which makes displacement and reflection maps, but they are actually just blurred greyscale maps. If you take a leaf with drops on it, but on the photo they reflect other leaves or something dark, the displacement is often just opposite as it should be and reflection as well. Or birch barks where the darks are actually often protruding, whilst the white is flat.
So I always check these maps and repaint if needed.