Why are objects missing from the Metadata Cache Manager? When viewing the Cache Manager Online, not all objects are displayed.
In order to reduce the storage of unnecessary data in CRM, the Metadata Cache Manager does not retrieve and store any filtering metadata for objects that are not supported. In some situations, some filter criteria may not be supported (For example: an unsupported Datatype or Operator) and the Metadata Cache Manager flags it as false.
CRM Help Documentation: Configurable Lookup Filters and Layouts