Earlier quoted context omitted.
Do you have a citation for that other than Quora?
No. It's something I heard growing up in SA, and I thought there'd be lots of sources about it online, but that was all I could find. It's possible that it's a myth - happy to hear from someone who knows more.
Right around the same time the Oppenheimers were becoming the wealthiest and one of the most powerful families in South Africa. Despite being ethnically Jewish, I've never once heard of them facing any discrimination from the apartheid regime or the broader SA public.