Nope, you completely misread the post. All Mac’s including M4s and M5s can run at a 1:1 4K resolution all day long filling the screen completely. That’s not what the OP wanted though, they wanted to render at 8k (roughly 7680 px by 4320 px), then downsample that by 2x in each direction to map to the 4K display. Supposedly to make things “look better” than rendering at the native resolution but it sounds insane to me.