Sounds like due policy making process has been followed by the CAA
Many of the posts here try to make this issue an experience vs inexperience issue or an ATPL vs CPL war and, whilst I think all of those points are valid, this issue, I believe, is one of wording. The manufacturer says single pilot under certain conditions and the CPL PIC limitations include no multi-crew operation or anything >5700 kg (I know there are sub-paragraphs to those and more)
Loop hole or not, which words set the legal precident? If a deceased passenger's family lays a civil claim against the operator, PIC and SACAA who is going to be accountable? This answer should come from CAA legal department, not flight operations.
It boosts operator's profits to employ a lower qualified pilot (who has less chance of getting into an airline) rather than a more qualified and naturally expensive one. To me, the question is not about whether boosting a handful of people's profits is safe or not, it is really whether it is legal or not.
The SACAA should be held accountable for its poor leadership on this issue. But then that would beg the question as to whether SA has an accountable government and for that matter can you really call it a democracy when a bad government is not voted out... but I suppose that is for a different forum.