I dont think that's how it works. Something developed for next gen consoles from the ground aiming to use whole next gen power cant run on older machine. Imagine spiderman , horzion or god of war on ps 3. They would need massively dumb down version for previous gen
This all depends on what the team wanted to do internally. If they from the get-go started out knowing that it was going to be an anaconda game, then that gives them a lot more freedom to do things.
But if the game started out as an Xbox one only game then the design doc is entirely different.
The thing is we don't know how it was built and when anaconda came into it.
The thing about game design a lot of people in these forums don't understand is that developers go into making a game with a design doc and have an idea of what features that they want to add and what things they want to accomplish.
New hardware gives them the opportunity to try new things, but it takes years for them to understand everything that they can do. which is why a lot of games that start out in the generation have vastly different and Superior sequels.
I guarantee that most games coming out on both systems day 1 likely started out as Xbox one and PlayStation 4 games.