YES, I got caught out on this "silly rule". Left FAJS on a BA flight to LHR. left with laptop and camera case (small) as hand luggage. No problem what so ever. Return trip back to JNB from LHR was altogether different. No way - one piece of hand luggae only, so I had no choice but to pack my nice expensive camera into my hold bound suitcase.
I agree that the "hand luggage" is abused by many travellers - bloody hell - if one is not first on board, chances of overhead locker space is slim.