Good to see. Moves in the right direction.
The ban will work better if South Africa completes it. That's to say, that South Africa denies entry to non-South African citizens [including Americans], so that all travellers, rather than merely the Biden ban's non-Americans, are targetted. The virus doesn't care which passport you hold. It will hop on a US citizen as easily as it will a South African.
If you have both bans, then the only group left to worry about is people with dual nationality.