Well, for what it's worth, I disagree with Gardyloo

My reading of the rule is that the phrase "travel to/from Europe in both directions" is concerning how you are getting from/to the continent of Africa via the continent of Europe-Middle East

And in your proposed itinerary at the beginning you get from Africa to Middle East (MPM-DOH) and at the end you get back to Africa from Europe (LHR-JNB)
So you are NOT travelling to/from Europe in both directions, and so the restriction regarding having South Africa/Mauritius in the itinerary does not apply

Unfortunately the on-line tool has still not been updated to reflect this new rule (which came in in April) so we cannot test Oneworld's interpretation of the rule.