Despite One Sword Stroke’s demeaning words. His true intention to not use his Transformation skill was because it was his trump card. In fact, Transformation skill is every player’s trump card. Only a few players would release information regarding about their Inheritance. The smart ones would not, tell everyone about your strengths, giving everyone a chance to exploit your weaknesses
A good example was Wei Yan Er’s Darkness Inheritance. Her Transformation skill maybe strong but she was extremely vulnerable to Holy elemental damage during the activation duration. If her weakness was discovered by outsiders, anyone could counter her with a bunch of Priests and Knights. On the other hand, if the Fire Immunity of the Phoenix is kept a secret, all dispatched Pyromancer will be completely be wasted.