We have been on the safari tons of tmes. The best ever ride was around dusk in the summer. The lions were out and the male lion was on "pride" rock just like the lion king. If that wasn't enough he let out a roar that was just unbelievable. The entire vehicle was silent. In fact even before we got to the lions we could hear him roaring. When we pulled away the guide/driver said that we just saw a rare sight. It doesn't happen that often.
As others have said it's just in the timing and luck. We have been riding the safari since opening week and very rarely even saw the lions and had never heardtje male roar. It was quite a sight.