Why is the cable used in the HDMI Sink minimum differential sensitivity test?

Why is the cable used in the HDMI Sink minimum differential sensitivity test?

In the Sink minimum differential sensitivity measurement set up diagram, a cable is used for connecting the HDMI-TPA-R-TDR and DUT. This is not mandatory. You can connect the TPA-P-TDR test fixture instead of the TPA-R-TDR and connect the TPA-P-TDR directly to the DUT. For some sink device the accessibility of the HDMI port using the TPA-P-TDR is not possible, in those cases you can use the cable to connect the TPA-R-TDR and DUT. However, at the end of the measurement you need to measure the differential voltage at the DUT end.