No problem man, I feel like if you are into this sort of sport, the best training is training that resembles what you are doing in the sport. The guy who wrote that article is no doubt an expert, but it's semi-irrelevant since you are probably not into bare-knuckle fighting, and if you do train to fight, your hands will be wrapped to protect your hands as much as possible for MMA. If you do not train to fight, kuckle pushups will be no harm to you. Just listen to your body. It will tell you what is right.