Earth's atmosphere is what is distorting the light coming from the sun. When the sun is setting or rising its light travels through a much greater distance of air (which is proximate to an observer). This is true for both spherical and flat Earth theories.

Because the atmosphere contains a large amount of water vapor sometimes visual phenomena mimic what we see when it passes through liquid water; sun dogs for example. Light is also reflected off of water vapor; bright white clouds, and this can produce 'God light', when rays of light spread out from between cloud layers. When the rays are traced upwards to a focal point it can look like the sun is proximate but it is only the reflected light source.

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