He is not the only top player who does this though. Off the top of my head, at Wimbledon Federer dropped sets to Benny and Malisse and djokovic lost one to Stepanek.
yeah difference is Fed and Djok drop by not playing their best. Murray drop sets playing his best, by the time the final comes his percentage all used up. Look at the s-final, tsonga took him out. Nobody can play high percentage every game. Murray need to reserve his high percentage game in the final as he is inferior player, hitting big and painting lines. Unable to do so due to opponents in front forcing him. Conclude he isnt smooth enough beating scrubs, still many efforts.