I dont live in Cape Town so I cannot speak with as much authority as you on the subject but Spaza was coined in Cape Town and I a**ume it was coined as a discription of the Xhosa vernac movement that was taking place in the Cape. Is this not correct?
I just spoke to Middle Finga before I started this paragraph. He tells me that Spaza is all inclusive. If cats use a mixture of different languages, eg: Zulu, Tswana, English and Afrikaans, it is Spaza. So Spaza is all inclusive. He tells me a lot of cats are not aware that they are doing Spaza because they have not heard the term (Pro etc), but they are cla**ified as Spaza. eg:if H20 had to go to Cape Town, they would be introduced as Spaza cats. He did, however, confirm that Spaza did originate in Cape Town, and was coined as a Xhosa based (but also including other languages) hip hop form. The definition has since evolved to include all types of tsotsi taal rap.
So it was coined as a Cape Xhosa thing and has grown to include everything else that is similar. So ya you are 100% correct. Im not sure, however, if the North West cats would term Cape Vernac hip hop as Motswako too.