I tested again on one of my iOS devices and still can't find any way to get the images to display in HDR. I can tell they were obviously captured better but they don't actually seem to exceed SDR in brightness.

Edit: I actually found that a small fraction of the images do display in HDR: the first cityscape image, the photo of the sunflowers, the second photo of the cityscape right after, and the first photo under "Film Meets HDR". Nothing else in the article is HDR, though.