I just had an idea - what if rather than zombies behaving like either of these specifically, they have dynamic behaviour? During the daytime they’d try to find shade or secluded areas if possible as opposed to areas with excessive light, but during nighttime they’d be attracted to it, potentially ambushing from the shadows.
Now, you could even flip it around so it’s vice versa, because this would present an interesting tradeoff - if zombies were not fond of light during the night, you’d be able to use lighting to ward them off, at the expense of being easily spotted by other players. Naturally, no matter how survival-centric UII becomes, PvP will still remain a constant threat, and there’s always going to be bandits out there (both human and NPC!) looking for easy pickings.
If you wanted to take it even further, this two-sided behaviour could be applicable to only certain zombie types. This would create an interesting variety that you’d have to take into account when planning on how to defend yourself against zombies - any given solution should not work on every type.