How project chartfields (PC Business Unit, Project ID and Activity ID) populated on the BI_ACCT_LN_S

My assumption is that it should be populated from BI_LINE_DST. But if a user has entered different project chartfields on Line - Proj Info page (BI_LINE.PROJECT_ID) which is different from the PROJECT_ID entered on accounting distribution (BI_LINE_DST), the Billing preload process(BIPRELD) override the PROJECT_ID on BI_ACCT_LN_STG table to the project entered on Line - Proj Info page (BI_LINE.PROJECT_ID).

What is the business logic for overriding the project chartfields.

Ideally project chartfields on BI_ACCT_ENTRY should be same as of BI_LINE_DST, irrespective of the value entered on BI_LINE.PROJECT_ID.