I am also unsure about the degree to which it was divination and the degree of memorisation technique. In The Cult of Ifá among the Yoruba. 1982. E. M. McClelland, page 56 according to my notes, which are not perfect, McClelland talks about the “sacrifice” paid to the diviner being a sheep or ram, cooked chicken or other items which help the priest stay alive.
From reading that and other books, I get the impression that the priest would use the divination practice to retrieve the relevant verses depending on the presenting problem. Some may be more hypothetical, some very practical, some spiritual, but the knowledge was attributed to the gods. There was talk of the way to treat smallpox and other illnesses, for example - much of it quite practical and rational.
My conclusion is that the readings were a mix of what we would call religion and what we would call science and what we would call psychology and what we would call fortune-telling and so on - depending on the client - the term McClelland uses.
The books I mentioned in an earlier post demonstrate that the systems were complex and many genres of knowledge interwoven. And I suspect that Western observers would only glimpse the full extent of the system.