So why is it rejected?
Just because they're still trying to use HDMI to prevent piracy? Who in fuck's name is using HDMI capture for piracy? On a 24fps movie, that's 237MB of data to process every second just for the video. A 2 hour movie would be 1.6TB. Plus the audio would likely be over 2TB.
I've got a Jellyfin server packed with 4K Blu-ray rips that suggest there are easier ways to get at that data.