I have already, yesterday logged a "support request" — have been issued with a case number — and am still waiting on a reply.
Have also called on one of the chief local [South African, reseller, DigiCape] but have not yet been able to secure a reply, to my specific questions, as I suspect they don't really have any answers, other than the "default" that I have already been getting pretty much everywhere, so far.
Just thought that while I was waiting, I would try here, to see if there have been any developments that have been made/discovered by some more hands-on users.
Hope I do come across an answer, as I can't see myself having the bundle of dough to replace the MacPro, as yet, especially in light of the fact that there is no realistic/logical explanation as to why the "lesser" of my two Macs able to accept the new operating system, while the "Beastly" one can't just because of some silly "model ID code, or whatever it might be causing the issue".
As I say, there is no immediately obvious, or physical/hardware shortage that is my making MacPro be rated as "worse off" than the MacBook Pro model that I own.
I guess I will have to keep on trying to see if I can get a reply, directly from Apple, or from wherever I may indeed get a logical explanation.
If I do, I will be sure to post that update here, A.S.A.P. - Just in case there any other users who may be experiencing the same grief and unexplained phenomena, as am I.