Are you claiming those things do not sometimes occur on a highly localized point, thereby allowing views of objects further in the distance, yet obscuring portions of, or even all of, objects closer to the viewer?
What exactly are you suggesting the horizon line is? Because it clearly isn't mist / fog etc in a 'highly localised point'.
The discussion is not about the horizon, Bob, but I am going to try and clarify.
Sometimes I can see an object ten feet in front of my nose.
Sometimes I can even see objects claimed to be millions or billions of miles distant.
Other times, I cannot even see my own outstretched hand, held level in front of my face, because of the weather; yet, If I simply turn my gaze toward the sky, I can clearly see the moon and some stars at the same exact time.
The horizon is malleable and is dependent on a lot of conditions and location.
If I was on an otherwise flat desert and a sandstorm was afoot a mile away, I wouldn't see anything 1 mile and 1 inch away, if it was behind that sandstorm, yet I could see potentially see an automobile three miles away if I slightly turn my eyes to the left or right.
The discussion is about objects you can or cannot see and why.
And I think I even need to take my own advice, and just keep it focused on this crappy placard.