Where did the Cape Party get its logo?

Yes, yes, I know. The election is gone. As is the Cape Party with their utterly miserable and rather embarrassing showing of about 1,400 votes. But then I just had a thought.
Hypothetically, should they win and declare the Cape independent, exactly where would the borders be? After all, while it roughly follows the borders of the Northern and Western Cape provinces, it’s certainly not exact – especially with that chunk of Eastern Cape coast included.

Well, it stands to reason that they would be wherever was needed to make the new state the (francesque) shape of the Cape on their logo, thus:

And that’s all well and good. But then I wondered where they had got that particular shape from. Did all three of them sit down and have a meeting about it? Was it a rough doodle? Or was there some other source?

And then I found this page on wikipedia, which featured this image and while observing the form of the (ironically) pale bit, realised that I need wonder no more:

“Map showing the proportion of the South African population
that self-described as “Black African” in the 2001 census”

But no – it’s surely just chance, right (even that chunk of Eastern Cape coast)?