Argus,
I don't know what Mr. Petter-Bowyer's background is, and I haven't read his book, but there is always a lot of misunderstanding about many submunitions, and this could possibly be some more.
Rhodesia didn't have much of a weapons development program, but South Africa did. I've handled some SA pieces similar to what you describe, and also have seen and photographed the dispenser. At least for the pieces that I am familiar with, they consist of a steel sphere, internally fuzed, which is about 100mm in diameter. The outside is wrapped in a rubberized sort of plastic, which could be related to this story. The ones I've seen most often are a green color, somewhat brighter than forest green. I'll dig into my files tonight and see if I can find some photos and maybe tech info, but if you/anyone has other hard tech info I'd love to see it.