Take whistle as an example—although it might not be an appropriate one.
Everyone could do it but not automatically. Cultivation was like a long process of learning to whistle. Everyone had this ability in them. They just didn't know how to use it without practice.
Although Himmel Soan told Viclan what his ability was, Viclan couldn't obtain the ability himself. To do that, one needed a spiritual foundation. Only then could one generate the spiritual essence.
Very few people were born with a spiritual foundation. It was mainly inherited and very hard to obtain through practice.
Most members of the three Himmelian divisions had a spiritual foundation through inheritance, which was why they were such formidable warriors. They were no longer ordinary people.
As the spiritual foundation was almost impossible to acquire, Himmel Soan could only introduce the principle to Viclan and let him figure it out on his own.