It should have similar behavior to the one in RadGridView https://docs.telerik.com/devtools/wpf/controls/radgridview/columns/column-groups
VirtualGridCellClipboardEventArgs.Cell.ColumnIndex is off by 1 if you pin a column to the left.
Same with VirtualGridCellClipboardEventArgs.Cell.RowIndex if you pin a column to the top.