Well, maybe, I think I get what you are saying, but I'm not talking about testing for omicron specifically (at least I think I'm not), I'm talking about total COVID case numbers (of whatever strain) in South Africa. As Daily covid case numbers seem to be shooting upwards, contemporaneously with the detection of omicron, I don't see what else would cause that other than Omicron being more infectious than Delta.
I think that "we don't know yet" is a good motto for this entire pandemic. But I don't see what's wrong with my reasoning above, based on the few days data we have since Omicron was identified. It still seems to me the evidence is that it's even more infectious than Delta - but clearly it's too early to be able to say if it's as severe, less severe, or worse. It feels rather anxiety-inducing waiting for that crucial aspect to become clear.
Your final point intrigues me, but is well beyond anything I understand about this stuff.