I was going to be snarky, but no, you simply don't know what is going on on either the CPU side or GPU side without metrics, so I would refrain from making claims like that. You don't know what is going on on each thread, what processes are running there and how much CPU time they are taking just by looking at a trailer. You need performance tools.
I mean, I'm sure there's a lot of stuff that can be cut out from the game or scaled down, but you simply don't know given that they are working with a very high baseline and designing their game around it.
What features can be scaled down and which ones need to be cut? And what can't be cut? In the case of Horizon, what if a low end PC can't load up the terrain on time due to slow SSD or worse, an HDD? What if the low end console has to cut out flying because the terrain can't be loaded fast enough? What if fluid simulation takes a significant part of gameplay and that needs to be cut out? What if the game simulation is too much for a jaguar CPU alongside all the draw calls it has to make? What if you have to remove/replace too many assets since you are working with ~13 GBs of high speed ram?
"EVERYTHING IS SCALABLE!!" is a marketing theme by MS, maybe it works, maybe it doesn't. Maybe you have to cut out so much the game is just way too different. I mean, you can "scale down" any game to an Atari 3600 by removing everything, but that's not the point.
If we are talking about the same game just with some settings turned down, with the same features, you WILL design the game around the old CPU and I/O, you just have to.