I believe that’s entirely an illusion (psycho-sensory distortion). Apparent size as you perceive it is bigger near the horizon but actual angle subtended is slightly less. There is no actual magnification at all.
If it’s just an illusion and there is no magnification, then why can we see features on a Harvest Moon with the naked eye that would normally require a telescope to see?
Chessplayer, It’s all in your head. Hold up a quarter at arm’s length and compare sizes. No difference. Sometimes I wake up at night and think I can see things in the semi-darkness. They aren’t really there. All in the neurons.