Actually, monstrousness implies the opposite of anthropomorphism, namely cosmicism. By definition, monsters deviate from norms, which is why in the movies they’re presented as inhuman. In the article, I simply apply most elements of the definition of “monstrous” to nature (from Dictionary.com): frightful, hideous, shocking, outrageous, immense, deviating grotesquely from a norm. There’s nothing in the definition that says monsters have to be human-like; it’s precisely the opposite that’s meant. That’s why H.P. Lovecraft used his monstrous characters to symbolize nature’s indifference to us.
In this other article, I explain in greater detail how the universe at large fulfills the criteria for monstrousness.