"Although a dragon only has one reverse scale, at least they are all dragon scales, and the quality is quite good."
The Apocalypse Heavenly Skeleton Armor required 108 True Dragon Scales, but each dragon only possessed one reverse scale – it was the first scale that the dragon's heart passed its blood through to the rest of the body, responsible for protecting the dragon's heart, and it was the hardest piece of armor on a dragon, each dragon having only one.
The 108 True Dragon Scales were meant to protect the array nodes of the armor, which could increase the armor's defensive power exponentially as well as support stronger forces.
Naturally, the present Cang Long could not possibly gather 108 reverse scales.