Orunmila doing divination in heaven for Obatala before the world is formed is interesting because it is also a divination prior to the establishment of the Ifa divination system on earth. The divination is prescriptive. It tells Obatala what to do.

It doesn't seem like we need to posit absolute interval between the divination itself and Orunmila telling Obatala what to do, considering these things don't happen in time. The divination is Orunmila "speaking".