The Crimson Binome
Hero
Actually, that skill does make special note of circumstances as heavily modifying the outcome.To give just one illustration of how inane the desire for your PC modelling tools to also be a world simulator are, because of this desire for consistency it is hardcoded into the rules of D&D 3.X that an equally skilled lawyer and barmaid will earn equal amounts of money because that's how the profession skill works.
And even if it did work as you say it does, so what? The results don't need to be realistic. This is a fantasy world with elves and dragons. It's not supposed to be realistic. The important thing is that the rules are consistent, and they must be consistent if we are to use them to model anything at all!
And if you (as DM) do not like the rules in any given area - if you think it's silly for a barmaid to make as much money as a barrister - then you can change them out for a more detailed model. The rules in the book are a simplified model of the world, taking into account certain assumptions, but that's not the same thing as being abstract; the rules do hold for normal circumstances that are likely to apply, and if those assumptions can no longer be safely assumed (as in your world curvature example), then that's why we have a DM there to intervene.
What would be insane would be to ascribe different realities - not just different scales of resolution, reflecting the same realities - to different characters, based not on anything within their world that could be a real distinction between them, but based on who is controlling them at the table.
If a wide variety of individuals with +20 to hit can each take between 10 and 30 arrow wounds without dropping, and even an unskilled novice with only +5 to hit can still take 3 arrows and keep going, then it would be insane to suggest that someone else with +20 to hit would die from a single arrow.
It doesn't need to be an OotS style of causal relation with actual levels, but the ability to hit and take a hit are clearly both linked to something that actually exists within the world (such as skill at arms, or actual combat experience), and whatever complex formula actually governs that stuff simply does not allow for anyone to drop from a single arrow hit.