Reference Field Default Value on Transaction Source, with wrong value

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We have noticed some of the standard Transaction Sources including Distributed Order Orchestration are setup for Reference Field Default Value as interface_header_attribute1 but the oracle documents say this field indicates which line transaction flexfield segment, i.e. RA_INTERFACE_LINES_ALL.INTERFACE_* field, you want to appear in the Reference field in the Transaction form.

In our case we see, the field called "Cross Reference" on the Transaction header carries Sales Order number which is not a interface_header_attribute1. Please help us to figure out the usage of this field and the value already populated here.