I thought that concept was for the moon. If, however, the sun were closer than the highest clouds, that could be described as much closer than 100 miles, and it would also mean the sun was well below the inner firmament, but you stated earlier (in this post) that the sun must be outside the firmament.
Do you agree that if the sun is anywhere above Earth (close or not close), there is a location on Earth that is directly below the sun, so that an observer at that location would have the sun directly above them? The location would vary, depending on the date and time, of course.
As can be seen, or viewed, by an observer on the flat earth, there are clouds behind and in front of the sun at one time or another!
It is inappropriate for anybody to simply say that what is being seen, or what has been seen, is nothing but an optical illusion, but that the sun is really 93 million miles away! The sun is not 93 million miles away, and if anybody chooses to believe that what is being seen, or has been seen, and captured in video footage and on camera being nothing but an optical illusion, then I have this to say to all of such people, I will say to each and everyone of you who believe in the optical illusion phenomena, that the sun itself is an optical illusion, it's not a physical manifestation but rather an illusionary one!