What does setEndEffectorLink (from moveit::planning_interface) do?

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My gripper is mounted slightly off-center from the tool on a robot arm, and I need some simple way to transform coordinates when moving the robot arm. I've set up a transform that is supposed to convey the offset, it basically goes in as a final link in the /tf topic (so we have base_link, shoulder_link ... ... ee_link, gripper_link). However using setEndEffectorLink does nothing, as it seems. I though that

group.plan()

would take the EndEffectorLink value as it's target, is that incorrect?

I've also tried using

group.setEndEffectorLink("nonsensesdkjhfsjkdfhsd")

and MoveIt doesn't seem to care. What am I missing?

Anyone?