I think also (and DF guys seem to bring that up) that there is some kind of barrier to using these systems to their full ability when just patching the old gen games. But then again Ghost of Tsushima and Days Gone (which is an UE4 game) did get 4K/60 modes with exactly that kind of patch, so who knows.
Ghosts of Tsushima is still 1800p checkerboarded on the PS5, it just went to 60fps with no other visual improvements. Days Gone I
believe went 4k 'native' (there's some contention that it's still checkerboarded but based on how it looks and the developers comments it seems it went native to me), but with dynamic res added as well. Either way they really didn't change their upper resolution, Days Gone perhaps as they went from checkerboarded to native.
Both are far smaller jumps than what would be required to take Fallen Order to 4k/60 from the previous mid-gen refresh consoles, for example Fallen Order on the PS4 Pro reached a max of 1200p in the 30fps mode (and that was the ceiling - it could go in the 900p range), and a max of 900p in the performance mode (which of course didn't come anywhere near 60fps locked).
Going from that...to 4k/60 would make it the largest leap of any previous-to next-gen patch released, significantly so - that's more than a 5X pixel count increase, and wanting better performance to boot. I mean I don't think the graphics in gameplay necessarily warrant these GPU demands, but it is what it is - you wouldn't get that without a major reworking of the engine.