The sixteen-cowrie system stands in a specific relation to Ifa within the same religious world, and the relation is about authority rather than about technique.
Ifa is read by the babalawo, a specialist whose training is long and whose office is restricted. The cowrie system is available to priests and priestesses of the orisha more broadly, which means that a house can obtain a reading without recourse to a babalawo. In practice the two are used for different weights of question, and lineages differ on where the line falls and on what the cowrie reading may not be used to determine.
That distribution of competence matters because it is the tradition's own answer to a question every divinatory system faces: who is entitled to speak for the powers. The answer here is institutional. It is settled by initiation and by lineage, not by aptitude or by study, and a person who has not been initiated cannot acquire the standing by learning the technique.
For that reason the atlas records what the system is, where it is practised and how it relates to Ifa, and does not set out the readings. This is a closed practice with living authorities, the meanings attached to the sixteen configurations belong to initiated priests, and a public account of them would be of no use to a practitioner and would misrepresent the tradition to everyone else.
Naming a practice as closed is a description of it, not an omission from the record.