The origin of the new South African plug is IEC 60906-1, which was created in 1986 and proposed, during the 1990s, as a replacement for all of the European grounded plug types, including CEE 7/4 (Schuko) the current British rectangular pin BS1363 type.

The problem was, while it's a nice idea and the plugs are neat and compact, it ultimately was seen as being a very expensive and disruptive solution in search of a problem that few people were having, as the vast majority of European countries either already use CEE 7/7 compatible grounded electrical sockets. Two outliers, Denmark are also in the process of migrating towards CEE 7/7 by adopting either 'Schuko' (CEE 7/3) in the case of Italy or the French/Belgian standard with a grounding pin CEE 7/5 (allowed in Denmark).

The present day European CEE 7 system works like this:

Sockets:

CEE 7/3 - 16 Amp 'Schuko' recessed socket, with side scraping earths - (Unpolarised) - Most Common type.
CEE 7/5 - 16 Amp 'French/Belgian' recessed socket, with pin earth - (Polarised) - Used in France, Belgium, Poland, Czechia and Slovakia.

Plugs:

CEE 7/7 - 16-amp grounded plug that fits both types of socket above, and has both earth pin receptacle on face of plug + scraping contacts - Standard on all modern grounded appliances. Used with Class I appliances requiring grounding and in many countries is the only re-wirable plug type sold, so you may find it wired with class II appliances, with a superfluous ground terminal.

CEE 7/16 - 2.5 amp non-grounded plug with springy pins that angle slightly inwards. It is only used on low powered appliances and also fits both of the sockets above. (It is also compatible with several now obsolete socket types, and non-CEE 7 systems used in Italy, Denmark, Switzerland, British Shaver Sockets and the modern South African system etc). - This is used with low power, class II (double insulated) appliances and devices like mobile phone chargers etc.

CEE 7/17 - 16 amp non-grounded plug, compatible with the two socket types above. This has cut outs that make it polarisable with the French/Belgian grounding pin, or may be symmetrical and non-polarised i.e. go in either way. (It is also compatible with several non CEE 7 systems: Denmark etc and obsolete non-grounded sockets). You'll often find this on hair dryers, vaccum cleaners and high power, class II (Double insulated) appliances.

Obsolete types:
CEE 7/1 - Non-Grounded sockets and CEE 7/2 non-grounded plugs. These existed in the days of Class 0 appliances and are banned in most EU countries in new installations.

Semi-compatible systems to national standards, nothing to do with CEE 7.
Italy - 10 amp sockets accept CEE 7/16.
Switzerland - 10 amp sockets accept CEE 7/16.
Denmark- 13 amp sockets dangerously accept all CEE 7 plug types, without connecting earth. This is an issue with Danish sockets, not CEE 7.

Additional safety features:

Recessed sockets (protect fingers) - required since the 1930s.
Shutters - increasingly required in most countries and mandatory in all countries using CEE 7/5 (French/Belgian) sockets.
Polarisation - implemented with CEE 7/5 but all European appliances are designed to be polarity agnostic, so it's largely irrelevant.
RCD protection - mandatory in all EU countries, beginning at various times from the mid 1970s onwards.
Grounding - mandatory use of grounded sockets is standard in most EU countries - start date varies from 1935 to 1990s.

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Being phased out:
Italy CEI 23-50: 3 pin sockets/plugs of 10 and 16 amp variety - replacement alternative is Schuko (CEE 7/3) or dual-standard sockets.
Denmark AFSNIT 107-2-D1 - 13 amp, 3 pin sockets - replacement is CEE 7/5

Systems being retained:
BS1363 / IS401 - Current UK/Irish sockets and plugs used in UK, Ireland, Cyprus and Malta.
These are use rectangular pins and interlocking shutters, and are very much physically incompatible with all of CEE 7.
Due to use of ring-circuits which require individually fused plugs, this type is unlikely to be replaced.

Swiss SN 441011 - Swiss Sockets
These are not being replaced, but are fully compatible with CEE 7/16 (Europlug)

But as you can see CEE 7 is very much the de-facto standard in Europe and it's just being enhanced with shutters and so on. From a safety point of view it works extremely well and is highly unlikely to be changed anytime soon.

I would suspect the problem in South Africa was a sense that CEE 7/7 is dangerously semi-compatible with old British BS546 type sockets, without connecting the earth.

However, I think logically speaking it would have made more sense for South Africa to have adopted CEE 7/5 (French/Belgian) type modern sockets with shutters and polarisation. They would have brought South African appliances into line with continental Europe and provided all the same benefits, albeit with a slightly larger size plug than what has been adopted.

The problem with the South African new standards is, while it's IEC based, nobody else is using it. Brazil also adopted a odd off-shoot of it, which is being used without sheathed pins and has been uprated to 20amps and is used with both 230 and 127V.

The other alternative, if you'd been going for something totally incompatible for safety reasons, might have been BS1363 (Current UK system) although I would have thought perhaps if it were adopted, the ring circuit wiring philosophy might be best left in England. It works fine with radials.