The pier does not reach the horizon. Which, contrary to Moana, you can't really do. The horizon stretches on a long infinite line. If you go east or west, exactly what you see is a perfectly straight line that you can build connecting roads or bridges between every continent or island in the world. The pier appears to pierce (say that out loud) the horizon but it comes short.
This is how the world operates. If you go east or west, you go in a circle, but anything you've build appears as a straight line. If you head north, you go to the center. If you go south you go outward.

You think it's a sphere, because you think north south loops. But it is like this dart board, except there is probably not an edge. It keeps continuing outward.
The boy is beyond the sun. Totally beyond, man.
Bravo
The pier is in front of the horizon.
So your attempt use it to say the posts didnt disappesr bottom-up is a either:
A: a lie to misrepresnt how circles work
B: you didnt realize an oject has to go behind something for it to be blocked from view.
Im gonna guess B, that youre a fucking moron