I'm not sure what the reasoning is behind forbidding elevated rail on Arig. You'd only need it to move oil around, so at best it forces you to not build on the island you start on, at worst it forces you to disassemble a partially-built base on the starting island once the player realizes they can't transport oil to where they are.
Even if you couldn't place elevated rail pillars on sand it'd be useful! It would allow you to make bridges where islands are close together, or at least a little bit further apart than underground pipes can reach. Then once you research arig's foundation, you would be able to place pillars on foundation instead of having to make long paths of foundation between islands to place rail on. Not that I think you'd ever do that now, since you would already be on an island with oil by the time you research that? I guess if your oil depletes and you need to get more?
