Here’s a concept that seems useful, but that I don’t remember ever hearing explicitly referred to (with my own tentative name for it—if it turns out to not already have one in some extensive philosophical literature, I might think more about whether it is a good name):
Normative reductionism: The value of a world history is equal to the value of its parts (for some definition of relevant parts).
For instance, if two world histories only differ between time t and time t’, according to NR you do not need to know what happened at other times to evaluate them in full. Similarly, the value of Alice’s life, or the value of Alice enjoying a nap, depend on the nature of her life or the nap, and not for instance on other people’s lives or events that took place before she was born with no effect on her (unless perhaps she has preferences about those events or they involve people having preferences about her, but still the total value can be decomposed into the value of different preferences being fulfilled or not). Straightforward hedonistic utilitarianism probably implies normative reductionism.
My impression is that people have different intuitions about this and vary in how much they assume it, and that it mostly isn’t entirely aligned with other axes of ethical view, either logically or sociologically, though is related to them. So it seems maybe worth noting explicitly.