If you are saying that it is not "Column built from other columns, behaves like tags", then I can't tell you why it doesn't work.
For me, calibre behaves as you describe if the column type is "Column built from other columns, behaves like tags", but works works fine if the column type is "Column built from other columns".
This attachment shows the definition of the column that works (#composite).
This attachment shows the definition of the column that behaves as you describe (#comp2).
This attachment shows calibre's output for both columns.
