Central Africa here means the equatorial forest belt and its margins, across what are now Gabon, Cameroon, the two Congos and Equatorial Guinea. The atlas holds it separately from West Africa and the Caribbean, and the separation is deliberate.
West African religion reaches the wider world largely through the Atlantic slave trade, and the shape it is best known in is the shape it took on the far side of that crossing: Yoruba orisha worship recomposed in Cuba, Brazil and Haiti, with a literature and a scholarship built around that transmission. Central African traditions crossed too, and left deep traces in Kongo-derived practice in the Americas, but the forest traditions of Gabon and its neighbours were not transmitted in the same way and are not organised on the same lines. Collapsing the two loses exactly the distinction that a reader most needs.
What the forest region is known for in the study of religion is initiation. Membership in a religious society, rather than adherence to a doctrine, is the unit; the society holds knowledge that is disclosed in stages; and a person's standing is a function of how far into that disclosure they have been taken. Ancestors are present and addressed rather than remembered, and the boundary between the living community and the dead is treated as traversable by trained people under controlled conditions.
Colonial administration and mission activity fell heavily on exactly these societies, because an institution that could not be read from outside looked like a threat.