Hi Chuck. There is a second version of the 'rule of thirds' than can sometimes be applied to landscape images and it is to try to ensure that there is something interesting in each third (usually the horizontal third for landscapes) of the image. If there is a single object in two thirds of the image, it should be twice as interesting as what is in the remaining third.
In the first two images of week 10, the bottom third is really strong so the sky, as dramatic as it is, is having a hard time competing.
In the third image, however, the top and bottom thirds have a compelling, but complementary focus to the center third, along with the dramatic depth of the scene, that makes the this image a clear winner. Excellent vision!