When object has both MeshRenderer and LineRenderer, and it's LineRenderer is set to "Use World Space" and LineRenderer is below the MeshRenderer. Then, when ToolHandle is in the Center mode, it will actually be drawn not in the center between the Cube and the Line, but only on the Cube's Pivot point. (looks same as in the Pivot mode)

To reproduce:
1. Open "Test" scene, from "LineRend_CenteredMode.zip"
2. Make sure "Tool Handle" is in Center mode.
3. Select "Cube" in the Hierarchy.

Expected result: Tool Handle should be in the middle between Cube and it's LineRenderer's line.
Actual result: Tool Handle is on Cube's Pivot point.

Reproducible with: 5.5.4p5, 5.6.4f1, 2017.1.1p4, 2017.2.0f3, 2017.3.0b4

Workaround:
While Cube is selected, in Inspector, move "Line Renderer" up, so it's above the "Mesh Renderer".
Now the Tool Handle is actually in the middle.