Most online accounts like that use Know YOUR CUSTOMER rules and they have to follow government rules regarding transfers.
In the first part, (hypothetically) Schwab might not have the ability to move money from a SA bank to their US subsidiary.
Second, transferring ownership of “shares” from one account to another is probably controlled by government regs.
Look at how difficult it is to transfer money out of China as an example of capital controls. Even getting cryptocurrency out of China is a pain in the neck if you are transferring from, say, a parent to a child student in the US.
There ARE ways around it. But, you need to be sure you are NEVER going back to where the money came from. They are not going to be “happy” about it. Even if you are leaving the US there are limits on what you can carry in gold and currency.
One way would be to have a business with foreign customers. Customers payments go to a bank outside South Africa and stay there. You pay local workers with local currency, and get local currency by for foreign currency.
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