You however are claiming something changes in the fundamental way something works at long distances, with no supporting evidence.
I'm not claiming that something changes perspective. Perspective was never really proven to operate on continuous trigonometry rules in the first place. I'm questioning the fundamental claims for how perspective works, and which there is no real evidence for.
Two points. If there’s no real evidence for how perspective works, then it’s not a valid proof of a flat earth.
Secondly, common sense says that if you have an infinitely long railway track, the tracks will appear to get closer together, to the point where they appear to touch. However, they will never appear to cross over. This can be proved mathematically, but I can’t be bothered as you can easily find the proof with Google, or common sense.
To expand on that, the sleepers appear to get closer and closer together as you get further and further away. We can see this for ourselves, so we don’t need any more evidence. Now, if we imagine a train running down the track, it gets smaller as it gets farther away. The rate of ‘shrinkage’ slows as it gets further away (think back, the sleepers appear to get closer together) but as the tracks never actually touch, to train never gets to the vanishing point. The tracks never appear to cross over. This also explains why objects far away seem to travel slower than ones close up.
This is your proof that perspective is well understood, whether you understand it or not. Like I said, Google the maths, or use common sense. Mind, you think all waves are bigger than heads, so I should stick to google!
As an aside, this explanation works on a flat earth.