Backport of !7651 (merged) for paraview/release.
For vtkCutter, point merging is not an explicit option. It is enabled by setting a vtkPointLocator that merges points. However, if a vtkNonMergingPointLocator is set as the point locator, then points will not be merged. Pass along the inferred merging option to vtk3DLinearGridPlaneCutter when execution is deferred to it.
(cherry picked from commit cbdb93fc)