If I was in a position to take advantage of this route, I would def jump on this fare. I have flown KQ in J JNB-NBO-BKK on their 787 and was impressed with the service provided. It wasn't SQ level (nobody else is really) but it far surpassed my expectations.
NOTE - connecting arrivals from JNB (and at least some other international arrivals as well) must clear security again at NBO. Since many of their international flights are banked together, the line can be lengthy, even for premium pax. I would be cautious about scheduling a tight connection at NBO. My 90 minute connection in J was barely enough and I doubt that the Y pax made the connection. I cleared security, walked to my gate, and boarding was already underway.