How to group DOO sales orders by a specific customer site

The main goal is to group DOO sales orders for customer site to Import Autoinvoice.

We have defined an autoinvoice grouping rule by LineAttribute13 (Profit Center Business Unit ) in the customer site, however in manage Autoinvoice lines the TRX date is defaulting to the order date/ship date, so it is grouping the AR invoice by order date/ship date even though the grouping rule is not defined by date, it is by LineAttribute13 which is assigned to the customer.