Resource Report - Parameters

Include Resources Active Between

Returns data for every history row where the resource is marked active. Rows where the resource was inactive are not included.

Cost Center

Only return data for history rows where the resource was in the specified cost center or child cost centers.

If checked, then resource history records are displayed in periods for which the resources were inactive. This is not very useful, and may be deprecated in the future.

Deprecating this may be a mistake. Support has seen a use case for calculating head count and you need inactive heads for that.