No, I did not consider that. That could be a fair criticism. I assume that all the target renders that we have seen so far have been on PC. So in this case, you believe the game is developed for current gen and upscaled to next gen?
I don't presume to know how they are doing it, actually. Stinkles would, I bet! I won't bother him about it, though, because I imagine that's getting into areas he can't talk about yet. Since the game has been in dev for something like 4+ years I can only assume that they started as an Xbox One title and built around that idea. Unless, they were given a directive to essentially launch the next system, given 2020 as a timeline to have it done, then they could have started to build out with the target specs I'm sure they knew before any one else on the planet and built down. Or, since they are such a huge team, they could have started on One arch, given that to their third party helper teams, and focused on a next-gen Scarlett vision.
I just have no idea. There are a lot of options, imo. It's kind of meta, but one of the most exciting things left to discover about Halo Infinite is this question. I do kind of think they were given as close to a blank check as possible in order to create this dual version vision. People talking about what the differences between a 'true' next-gen game and current gen might look directly at Halo Infinite to see what can be done, what limitations there are, etc.