Direct costs of an asset such as an S3 bucket is in a perspective's "Assets Not Allocated" group and it shows as such in the S3 Cost report. However, Cost History report is showing the same S3 bucket as allocated to a group.
The difference comes from the fact that the Cost History report applies the "fallback" mechanism while individuals reports such as the S3 Cost report do not apply fallback.
The fallback in Cost History report is a second check. It checks first if the asset is not allocated to a group, than it checks a second time if the account that owns the asset is allocated to a group, if yes, then move asset cost to group based on account.
Direct Cost: These costs have a resource ID or asset ID associated with them. The platform can attribute these costs to an asset or resource and can therefore allocate them to a Perspective group.
Indirect Cost: These costs are not associated with a resource ID or an asset ID. Support costs are an example of indirect cost. Therefore, they cannot be attributed to groups.
The platform classifies an AWS or Azure Service as a Direct Cost or Indirect Cost. When AWS or Azure introduces a service, the platform initially classifies the service cost as an Indirect Cost. When support for that service is eventually built into the the platform, the service cost becomes a Direct Cost that can be allocated to Perspective Groups.