Their exact degree below the equator is irrelevant because the point is not where at in the sky the constellations rest relevant to each other; the point is that you can see the same constellations at all.

Well, as the examples you gave show, if you're in Christiana (South Africa) you can't see the Southern Cross at the same moment that someone in Auckland (New Zealand) can see it. So each city's exact degree of latitude below the equator clearly is relevant!

I get the feeling we're at cross-purposes here, so will drop the subject and wish you well with your inquiries.