Oracle Cloud Tenancies once configured initially will take longer to display the full 12 months of cost data than compared to the AWS / GCP Clouds.
The current expectation is that a medium sized customer - 800,000 to 1,000,000 in spend will take 6-7 days to process and display costs across the full 12 month period available in reporting.
Customers with lower or higher amounts of spend than indicated above may see differences in timeframes for data to populate.