And
that is a useful set of information to add to the discussion.
I'm not sure how accurate size is as an indicator of species for feces, given that some dogs are quite large with large feces (and some many humans have small feces for dietary reasons), but it's not like the original commenter explained in much detail how they classified the feces either (other than indicating it was through images for many).
Edit: Regarding your second link, I have a pair of 65 pound dogs, and their poop is generally about 1/3 to 3/4 that size. I assume it could be a ~100 lb dog, but agree it's more likely from a person.