The golden-robed old man knew Gin's soul energy had reached the white-soul stage, even so, he couldn't find how Gin's doing that—not even with the few hundred years of his knowledge.
In truth, things aren't as complicated as the old man believes. Gin was controlling the herb using his soul energy, weirdly no one could sense it.
It's a fact if a soul master uses their soul energy another soul master at the same level could notice it, but this doesn't seem to be the case for Gin.
Otherwise, the old man would have perceived Gin was using his soul energy. The problem is, he couldn't.
After the 13th hidden seal discovery, his soul energy's attribute transformed into something unique, completely different from others. And, Gin himself hasn't realized this change.
