What do you see in that image?
Upon closer inspection of the picture (zoomed in), you can clearly see that the image is not of a straight line. The three rightmost columns of pixels have a clear antialiasing pattern suggesting further curvature.
This is the difference between your thought experiment and the Earth. Even in an experiment you carefully devised to "prove" a thinly-veiled point, you left some evidence to be found and analysed.