Ok let's make this simple.
If you walk away from an object, does that object look smaller to your view compared to what it looked like when you were closer.
Just answer that instead of trying to make out I'm saying it is physically smaller.
It subtends a smaller portion of my angular FOV.
This is commonly stated as it appears smaller.
But there is no actual compression, and when viewed and comprehended in context, it is actually just far away.
Not small, far away.
But why not actually make it simple, unlike all the complex nonsense you have been trying to avoid reality?
When you look at a distant tree, through a level tube, how does the light from the bottom of the tree reach your eye?
Does it just go from the bottom of the tree and straight to your eye?
Make the tree smaller.
Why?
It is the tree's physical size.
It shouldn't need to be made smaller.
If you need to make it smaller to argue your point your point is not describing reality.
You should be explaining how the light from the tree reaches the eye.
Or was this closer to it?
You're starting to get somewhere. It just needs tweaking.
And that somewhere is clearly quite disconnected from reality as now the tree is floating in mid air and crushed to a tiny portion of its actual size.
You see that big angled vision like a torch beam you put up from tube to tree...right?
That's you looking wrong.
No, that is just you completely missing the point.
They show the limits of the FOV of the tube.
Light within that region can reach your eye.
Light outside that region would be blocked by the tube.
But here, is this better:
No cone, just a line of light coming from the bottom of each tree.
We can even see that the light is the colour of the tree.
And a close up of the tube
So we can see the light from the distant tree manages to make it inside the tube and reach the eye.
The light from the bottom of the close tree instead hits the bottom of the tube, and as it can't go through the wall of the tube, it doesn't reach the eye.
The ability to see the tree is based on if the light goes into the tube, or hits the wall of the tube.
Doesn't get much simpler than that.
You can even show the mirrors using the same honest method:
The image from 2 reflections takes up a smaller angular span and thus appears more distant (far away, not smaller).