What I think the fellas are trying to draw your attention to (however tersely) is that the catalog page says "Mixing.... multiple line to multiple line." The multiple gives it away, as does mixing, which requires that several inputs be combined in a single output. Since the rated impedances are the same for input and output, you can use either as input or output.
I have one on the shelf at home. I've been meaning to create a simple problem solving box with it, e.g., balance/de-balance/pad any line as needed.