So, you don't know why it happens?
Why should it matter any more than should the temperature of Uranus matter?
This is not really a topic of discussion. If you can show that this is some kind of round earth proof, we would look into it. When we are asked what puts the sun into motion, for example, the standard reply is that the mechanism is presently unknown to us, but the motion is apparent. We base knowledge on empiricism here, not wild theories.
Ok, so Tom, let's change the narrative a bit.
Say a person out of genuine curiosity asks you a question about an observation, for instance an observed change of angular size of a celestial object, right? Can you just answer what causes this instead of saying "that's not important". Obviously, it's important to this person and he or she is asking what he believes to be an authority on the subject, namely the people who are supposed to be able to answer this.
Forget about hostility, this is a genuine question. I mean, if you don't know simply just say "I/we don't know". There's nothing wrong with that. But you can't say "I fail to see why this is important". An observation has been made and someone is asking for an explanation from the very people who are supposed to be able to answer.
Let's even assume flatout were undecided on the shape of the earth or the model that describes our solar system. He now knows how one model explains that particular phenomenon, he's seeking an explanation in regards to another model.
I'd like to know this too to be honest.