Sorry mate but honestly, you are mistaken. This is schoolboy geometry.
Let's suppose for a moment there is an imaginary 100 foot wall all the way from one side of the pitch to the other, standing right on the by line. And imagine the ball is where Sterling is about to kick it, and we are trying to work out if the ball is touching the wall, or if it is beyond the wall and there's a 1 inch gap. Got that in your mind? Now hold that thought for a moment.
Now imagine you're in your kitchen and imagine a ping pong ball on your kitchen table and you're trying to work out if the ball is touching the table or not. Possibly it is but possibly it's balanced on a grain of rice. You get your eye down to table level and have a look to see if the ball is touching. It doesn't matter from which side of the table you look, does it. It's the same view from any side of the table, so long as your eye is in line with the surface of the table.
Now go back to the football pitch and the wall. The wall is the table. It doesn't matter where along the wall you want to look from, the view is exactly the same. Above, at an angle, lying on the pitch, up in the stands, anywhere you like. So long as your eye is level with the by line and you look along the by line, you can view from any height and you get the same view of the ball and the line.