Running latest OctaneRender™ for Blender 2021.1.1 - 25.0 [TEST] build.
I don't think it's an expected behavior. When you're changing Image Texture node modes from default Wrap Around to Black Color or any other mode it works in a Color channel fine. But when you chain it with Texture Displacement node is ignoring those setting and as it looks it's always using Wrap Around by default.