If I stand on the beach I am taller than the water below me. Whitecaps on the water can still obsure my vision of far away objects.
Not if you're higher than the whitecaps.
An obstacle can only obscure more of an object beyond it than its own height if your eye level is below the height of the top of the obstacle.
Three scenarios shown below.
Top, your eye is below the level of the obstacle, more of the elephant than the obstacle's height is obscured.
Middle, your eye is level with the top of the obstacle, the same amount of elephant as the obstacle's height is obscured
Bottom, your eye is higher than the obstacle, less of the elephant than the obstacle's height is obscured:
That's the theory, here's my real life experiment demonstrating this:
Here's the set up:
Here's the 3 scenarios: