Agreed. In this case, I wonder how much that bleed at reasonable input levels is contributing to distortion that wouldn’t be present on a single-channel test. With the bleed being ~40hz and below, it may not have much audible impact when the unit’s used as a multitrack device, but it seems like there would be significant low end additions/cancellations when used as a stereo DAC.
Browsing other forums, it appears this is likely a design problem with the UMC series, as opposed to a bad unit. Still, I’m surprised more people who use it with a DAW aren’t alarmed when ALL of their input meters are going bonkers from one line-level input.