It's my belief that there aren't any 'true' flat earthers. Just a small group of ppl who enjoy extending and defending a nonsense idea to absurd lengths, and, of course, winding others up while doing so. IOW, I think it's all an 'in on the joke' thing.

Terry Pratchett does something similar of course in his DiscWorld series. I wonder why ppl can enjoy it in that context but get annoyed with ppl doing it outside of a story book? It's not like anyone gets harmed by ppl arguing (in my opinion, playfully but with a straight face) for a flat earth.

The fish-eye lens argument that you reference for example is plainly ridiculous, but also mildly amusing.