Search within specific month

This could/should be done as a measure probably, but here is a column expression that should work.  Not sure if you are checking all KPIs within the month or within a given KPI for that month, but both variations shown.

month_status =
VAR vPrelimRows =
    CALCULATE (
        COUNTROWS ( table ),
        ALLEXCEPT (
            table,
            table[Month]
        ),
        table[Status] = "Preliminary"
    )
RETURN
    IF (
        ISBLANK ( vPrelimRows ),
        "Final",
        "Preliminary"
    )

replace Table with your actual table name.  If you are looking within a KPI and month use

ALLEXCEPT(Table, Table[Month], Table[KPI])

Pat