As, according to the docs, this is
True if the node’s parent chain connects back to the document root node.
This is (in my opinion) expected behavior (as the node still connects back to the document root node, may it be visible or not).
While I agree that it seems strange to generate SceneNodes off-canvas, I think there’s nothing wrong with it, by itself. Those limits (and the behavior) should probably receive better documentation, but I think there might be some use-cases where this is useful (e.g., to not entirely delete nodes, but put them off-canvas).
Therefore, I would argue that yes, the documentation should be more clear about this, but I wouldn’t agree that this belongs in the “Bug” category…