Idk...reading the article it sounds fairly understandable. There are a lot of certain small animals in the area that dogs would like to chase. They run after the scent and get confused thinking that it's not a far drop or that the ledge is wider than it is. So it leads to a number of unfortunate accidents.

I think of it like this...have you ever gone down a set of stairs with an odd pattern to the carpeting making it difficult to see where the edge of the step is? There are all kids of perspective tricks and such our eyes can have difficulty with.

Edit: Plus some dogs are just stupid and will jump off of high things not realizing they will be injured on the way down. I love my mom's dog, but she is a moron and has jumped off of high places that could injure her. I have had to stop her from hurting herself on more than one occasion...and one time where I was afraid she was going to jump out of a second storey window from excitement. My brother's dog also has jumped off of a second storey balcony before. The dog was fine and was monitored by the vet hospital afterwards but yeah...some just aren't super bright either.