When you hold down the control key and drag a selected range of cells what is attached to the pointer indicating that the source contents are being moved?

Using Ctrl with drag, will copy not move the cells. You will see a cross beside the pointer. If you want to move them, put the mouse pointer on the edge of the cell or selected cells and do a drag without pressing any other key. You will see a cross, with an arrow head at the end of each of the 4 points on the cross.