on the video side, there are often the option of connecting the HDMI out of the source device directly to the display and a second HDMI out to the AVR/AVP for audio
This option is not available on monitors.
I will give you one simple example where additional 8 Gbps makes a real difference In everyday life.
You might have heard about new Samsung OLED monitor announced at CES. It's Odyssey Neo G9, 57-inch ultra-wide flagship 7680x2160p 10-bit 240Hz monitor. To see fully speced image on it, it needs to be fed with roughly 137 Gbps of video data. No single port can provide that much nowadays without using DSC codec.
Now, using the highest compression ratio 3.75:1 for DSC, the full spec image for this new monitor can fit into 48 Gbps port, but it cannot fit into 40 Gbps DSC pass-through pipeline. So, you need a full speed HDMI port to run this monitor with out of the box image.
If you connect this monitor to current AVRs, image quality will have to be compromised from RGB/444 to 422 chroma, and its non-standard resolution and refresh rate might not work at all. This needs to be fixed in future AVRs:
1. Full speed HDMI ports
2. More custom resolutions and refresh rates supported, beyond standard TV parameters.
It's a business case to be made for AVRs to become more appealing devices in new markets. Let's be honest here. Almost every single AVR and AV processor with HDMI FRL ports in last two years has been aggressively marketed towards console and PC gamers who happen to use 4K TV for gaming.
This strategy can bring you just as many new and easy customers. If AVR companies really want to penetrate PC gaming world further, those AVRs will need to become more friendly in connectivity with monitors, which are more diverse than TVs and require longer listings in EDID. And, growing number of those monitors require full speed ports for fully speced image to work, compressed or uncompressed.
At the end of the day, there shouldn't be any stubbornness in AVR circles not to provide full speed ports, when Nvidia, AMD, Intel, LG, Samsung, TCL, Sony and other TV and monitor makers routinely provide 48 Gbps ports on source and sink devices. Would you agree?