Like many things in SA, the only reason circuit breakers are wired upside down, must be because some person decided to make it like that many years ago, and so the fuchs, which became heineman which is now CBI, which dominated the SA market for many years. Unfortunately they have priced themselves out the market. You can tell those breakers are really old, by the exposed contacts, you cannot touch live contacts with a standard test finger on any new circuit breakers.

SA does things backwards, if you look at quality circuit breakers, like ABB you will notice the terminal for a forked busbar (which by the way works way better than a pin busbar, it frees up the terminals for the wires which reduces the chase of loose connections, which is very common with cheap mcb's which allow the wire to be inserted behind the plate) is at the bottom.

An mcb marked line and load will always take preference.

I think it is silly that we still feed into the top of the breaker and out the bottom, especially now that twin+e is the prefered wiring method.

In all my solar installs I wire into the bottom of the main switch and out the top (unless I use a main switch labeled line/load , which doesn't happen), the reason is because it saves the bridge wire from the bottom onto the top of the circuit breakers, it was done like thing for many many years, once again someone replaced an old green double heineman main switch with a newer style main switch and so all the sheep followed.