It’s fine for a quick hookup of an old PS3 or XBOX 360 in HD. But, at 9Gbps, not even the 18Gbps of HDMI 2.0, anything in 4K @60Hz will be color subsampled to 4:2:0 in 8 bit color. But, at least Onkyo isn’t pulling that s#%t around back like Sony.
While Denon and Yamaha don’t offer a front port on their flagships at all, they do have seven HDMI ports around back to Onkyo’s six and somebody could just connect a cable to the seventh port and have it on the ready for any temporarily connected devices with access to full bandwidth.