Why aren't my results being filtered by the members from my [Group Hierarchy] returned via the filter() statment below?

    SELECT 
    NON EMPTY {[Measures].[Group Count], [Measures].[Overall Group Count]   } ON COLUMNS,
    NON EMPTY {
        [Survey].[Surveys By Year].[Survey Year].ALLMEMBERS * 
        [Response Status].[Response Status].[Response Status].ALLMEMBERS} 
    DIMENSION PROPERTIES MEMBER_CAPTION, MEMBER_UNIQUE_NAME ON ROWS
FROM (
    SELECT ( { [Survey Type].[Survey Type Hierarchy].&[9] } ) ON COLUMNS
    FROM (
        SELECT ( { [Response Status].[Response Status].[All] } ) ON COLUMNS
        FROM (
            SELECT ( STRTOSET(@SurveySurveysByYear, CONSTRAINED) ) ON COLUMNS
            FROM (
            SELECT(filter([Group].[Group Hierarchy].members, instr(@GroupGroupFullName,[Group].[Group Hierarchy].Properties( "Group Full Name" )))) on columns 
            FROM [SysSurveyDW]))))

CELL PROPERTIES VALUE, BACK_COLOR, FORE_COLOR, FORMATTED_VALUE, FORMAT_STRING, FONT_NAME, FONT_SIZE, FONT_FLAGS