As what Oracle Support suggested, this would have to go by an Enhancement Request to Oracle FAW Idea Lab

SR 3-33605888811 : Column Selector Using Parameters in Oracle Analytics doesn't Aggregate Numbers Correct

Dev team went through the test case which I created internally to reproduce your issue. Dev team responded as follows -

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The problem is the grain of the query is altered with that case statement.

The non working case (report with the calculated column based on the parameters) is pulling every when clause from the case for aggregation.

The working case (report with the direct column) is pulling only 1 direct subject area column.

Unfortunately, there is no solution here.

we don't have the ability to reduce the case statement today.

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Since this is new feature introduced in OAC and it never worked in the past. This is not considered as a regression to code or not considered as a bug.

As an enhancement request to the code - The feature can be implemented as an optimization to fold the case expression on the argument supplied which will have same effect as the direct subject area column

We request you to raise an idea lab request from your side following this document - How To Create An Enhancement Request In Idea Lab For Oracle Analytics ( Doc ID 2662737.1 )

We can conclude this SR as an enhancement request to Oracle Analytics - DV product.

Hope it is clear.

Thanks & regards,

-Rajesh P.