plsql:DecodeFunctionUsageCheck wrong behaviour in group by

Hello
With Sonar version : Developer Edition Version 8.9.1 (build 44547)
We detected that rule suggesting to use case instead of decode that was improved following my previous request (see SONARPLSQL-726) does not have the same behavior in SELECT section than in GROUP BY section of a query.

In SELECT section last version of the rule (after SONARPLSQL-726) is working well and considers acceptable the usage of a “simple” decode.
But the same decode in the GROUP BY section of the same query is hit by the rule.

I guess this is something missing in the implementation of the SONARPLSQL-726.

Code to reproduce:

SELECT
    count(emp.first_name)                          as number_of_emp,
    DECODE(active_flag, 'Y', 'Active', 'Inactive') as status
FROM employee
GROUP BY 
    DECODE(active_flag, 'Y', 'Active', 'Inactive');

Thanks
Sebastien.