It doesn’t need to travel over HDMI. That to move signals from one device to another. If the hardware that is outputting the display signal itself wants to insert other data into the signal it’s receiving, it can directly. It doesn’t need to send it through another cable. It’s probably modifying an signal received through HDMI (or other cable), but it doesn’t need to send the modified signal again.
It doesn’t need to travel over HDMI. That to move signals from one device to another. If the hardware that is outputting the display signal itself wants to insert other data into the signal it’s receiving, it can directly. It doesn’t need to send it through another cable. It’s probably modifying an signal received through HDMI (or other cable), but it doesn’t need to send the modified signal again.
I’m just stupid and not thinking.
This sounds like the mental math I did, but I forgot to carry the reality.