of course it does something.
in vm2, you could not override a single customfield, you had to override all. That had the effect that the whole pattern idea did not work. You had to overwrite all customfields to change one => you copied all customfields and changed one.
The tool removes any customfield of a children, which is the same as the one of the parent. If you do not want to display the customfield of the parent in the child, use the disable checkbox at begin of the line.