Germany with its large population might not be an ideal place to fly
black aircraft- even at night. So, testing a plane in South Africa
might not be out of place.

Actually South Africa and the seas surronding it were traditional testing
ground for post WWII German advanced weapons.

If you check the news of 70s and 80s,you will find several reports of
unexplainable events taking place in seas off South Africa.

BTW A couple of years ago in very same area an USAF transport plane collided
with a German transport plane.This event was strange enough I guess.