"For foreign tourists in the second group who reported to immigration authorities for a 30-day extension after their visas expired on March 26 or thereafter, their visas will be automatically renewed every 30 days until the pandemic subsides, said Pol Lt Gen Sompong."
What is relevant about March 26? Basically, if you renewed before March 26, then they want everyone back in for another round?
If I go to apply for a 30-day extension (suppose I have a letter, but it's generic and it's unlikely that they'll accept it, but I choose to apply anyway) and I'm rejected, do they give me a 7-day extension by default?
See #3 of this post. You need a letter from the South African embassy with your name on it asking for a 30-day extension because you cannot return home. There are a lot of posts about this in this group.