I'm guessing relative to 1080p. Meaning, in this case, the need for 4k media blu-ray and displays. If upscaling to 4k on 1080p display the device will want to revert to its native resolution. So, 4k needed along the pathway from media to source player, AVR to display. Good question for Yamaha support regarding the RXA2020, that being any AVR limitations from analogue sources to HDMI output.
Maybe another example of receiver manufacturer feature set that may not be relevant given current standards.
Is 4k really needed for typical household HT setup ?
Anthem MRX500 [Processing] | Audio Refinement Multi 5 | OPPO BDP93 | Focal Chorus | JLAudio F110 | 50" Panasonic Plasma | Primacoustic Wall Panels