Is there a way to restrict exported data just to the columns that the user made visible?

I know that there is a possibility to always prevent a column from being exported ($col["export"]=false;) and there's a demo (export-selected.php) that, judging by the grid's header ("Export Selected Rows/Columns"), is supposed to do just what I'm looking for – but unfortunately the demo only honors selection of rows, and always exports all columns (regardless of which are selected/visible.)