'WF_ITEM_ATTRIBUTE_VALUES' used to store the attributes value for a Order Header and Lines workflow.
Or Shall I Say any Process that has workflow will have values inserted in this table (Unless worflow has no attributes).
When you create order with order Import, It insert the data in Order header and lines and at the time of Inserting data into header and lines it triggers the Worflow process and insert data into
WF_ITEMS
WF_ITEM_ACTIVITY_STATUSES
WF_ITEM_ATTRIBUTE_VALUES
etc
