On three points, the open-set families `[0,1,6,7]` and `[0,2,5,7]` are incomparable topologies: each contains a nontrivial open set absent from the other. Closing their union under finite intersections and arbitrary unions produces every subset bitmask, so the least containing topology is discrete. By contrast, `[0,7]` is a topology contained in both inputs. The open set with bitmask `1` belongs to the generated topology but not to this common subtopology. Thus existence of a common contained topology answers a different order question and cannot establish the unique least topology containing the inputs.
