SQL Server - moved index behind PK constraint to different filegroup, but space not freed
Space in FG2 used by objects:

SELECT DS.name AS FileGropName 
      ,OBJ.name AS ObjectName
      ,IDX.type_desc AS IndexType 
      ,IDX.name AS IndexName 
      ,AU.type_desc
      ,AU.total_pages * 8 / 1024 AS Mb
FROM sys.data_spaces AS DS 
     INNER JOIN sys.allocation_units AS AU 
         ON DS.data_space_id = AU.data_space_id 
     INNER JOIN sys.partitions AS PA 
         ON (AU.type IN (1, 3)  
             AND AU.container_id = PA.hobt_id) 
            OR 
            (AU.type = 2 
             AND AU.container_id = PA.partition_id) 
     INNER JOIN sys.objects AS OBJ 
         ON PA.object_id = OBJ.object_id 
     INNER JOIN sys.indexes AS IDX 
         ON PA.object_id = IDX.object_id 
            AND PA.index_id = IDX.index_id 
WHERE DS.name = 'FG2'
ORDER BY AU.total_pages DESC