Looked at their (Volharding Game Ranch) hunting rules: 50% of trophy fee for missed shots on large game, ie kudu, eland, buffalo, and 100% trophy fee on head shots that are missed with no resulting blood. Better make sure you shoot straight and don't miss. Take a look at their rules. I have not seen or heard of this before. I can't believe this would be a normal practice?
Separate note: John Henry at Greatland Safaris has great nyala. 12 + taken on his place this year - as he breeds nyala and are abundant on his place. Largest one taken this season was 28". I am not affiliated with them, but they are my outfitter/trusted friend of choice. Best wishes in your quest!