Well, clocks are just mechanical sundials. Before clockwise, there was sunwise (or deosil), and clocks' movements are based off of the movement of a shadow across a sundial.
Yes, when you are in the northern hemisphere, a sundial shadow falls to the north of the gnomon (the thing that makes a shadow). This makes the shadow move from the northwest to north to northeast over a day, which is clockwise. In the southern hemisphere, the shadow from the gnomon falls to the south, so it starts in the southwest and moves to the south and then southeast, which is anticlockwise.
The most obvious way to see this is the photo of the sundial in Perth, where the hours run anticlockwise.
Northern sundials (both vertically mounted and horizontal versions) need to be pointed North, whereas Southern sundials need to be pointed South. The article is stating that Southern horizontal versions can be mounted vertically in the Nothern hemisphere but must be pointed South.
I hope that helps, I had to re-read it a few times, myself.