To get a full reporting overview it would be needed to also show the Add. Currency fields in the Project plan as well as in the Project Budget entries, like in the Project Ledger entries and the General Ledger entries.
This resolves the issue to get an overview of the project entries where a project is managed in a currency separate from LCY.
If Add. reporting currency is not used the fields are empty, why the impact on performance for cases where this is not applicable is limited.