Because according to you, the moon's orbital motion in half a second is significant enough to impact the results. If that's the case, the moon should significantly move in my telescope while it tracks at a sidereal rate in the half second span of time it takes ISS to cross the moon.

You are a dramatic example of the Dunning-Kruger effect. You don't understand your own ignorance and you have the gall to insult me. This, my dear dumbass, is how much the moon moved in its orbit in half a second while my telescope tracked at a sidereal rate:
:moonorbitmotion:
Now, go on and try to convince people that the above motion is not negligible. Good luck.