I'm unclear why the 21 couldn't have a ceramic ball as a lock interface like the inkosi. Is there a technical reason? Is there some people who think there's a benefit to not designing it this way? Same for the pocket clip placement. I think the Inkosi is superior in pocket clip location.
Regarding the handle and blade shape, I think that's personal preference but I do like the looks of the Inkosi. What I don't like about the Inkosi is lack of a pivot bushing. To me, the pivot bushing is what makes the sebenza special relative to most other folding knives.
I'd like to see a pivot bushing offered as an option for every folding knife in the CRK lineup. Bushing-based Umnumzaan. Bushing-based Inkosi. Sign me up!! Still keep the non-bushing versions for people that prefer being able to loc-tite and micromanage their pivot tightness.