South Africa has three capitals but they have different roles: Pretoria is the executive/administrative capital, and this branch of the government is run by the head of state. The other roles are the legislative (Cape Town) and judicial (Bloemfontein) capitals. I would assume depending on which branch of the government is delivering news they would use the appropriate capital, but it’s most likely to be Pretoria.

Feel free to correct me I am not an expert or South African.

Sources: Wiki Executive power