I'd also like to point out a certain difference in the flat earth philosophy when regarding to the claimed magnification phenomenom.
The most common argument for a flat earth I ever hear (not only on this forum, there are several out there) is that it looks like so. And yes, it does. There have surely been a lot of ancient civilisations who believed in flat earth, and why not: from each of their perspectives, that has probably been a reasonable belief.
But I seriously doubt that any of them would have believed in a sun that circles endlessly above the earth. No. When they have seen how the sun seems to go behind the horizon, they have believed that that's what it really does. During the night it then moves beneath the earth (and whatever structure there is supporting us down there allows it to do so) to the other side. Or maybe the sun only lasts for one day, and the gods or whatever they believed in makes a new one for each day. But it surely doesn't stay above the earth forever: that would clearly be against their senses.
It is only this modern day theory (and I consider Rowbotham a "modern day" person in this context), that on the other hand says that we should trust our senses more than "unproven" theories and that the earth is flat, and simultaneously claims that the sun circles above the earth which it certainly doesn't seem to do. It labouriously makes up a theory about perspective and magnification in order to make it look possible, but still that seems to contradict anything we know about perspective and magnification in a closer-to-earth context. Making up a theory like this is really opposite to this entire philosophy.
Of course, this needs to be done. Unlike ancient civilisations, we know that the earth is large, something they had no idea about. We know about the existence of Europe, two Americas, Asia, Africa, Australia and so on, we probably have friends living in several of those, we surely know that the sun shines in different times in different places. This is when the reality tells us that our common sense is wrong. This is when we need to fabricate a new theory to make the reality fit in. And, frankly, some do this better than others.