Huh ? You do realise that the apparent motion of the moon over a given day is because of the rotation of the earth, and that the changes in the relative positions of the sun and moon, and hence the lighting conditions of the moon, are negligible ?
But then it wouldn't be sunset anymore. I understood the whole article to be about things you can see at sunset.
But a full moon can't rise to it's zenith at sunset.
But if it did, then it would be a half moon.
Of course not, because the sun is much further away than the moon.
If the moon is directly above you, and the sun is directly in front of you, they are at right angles from you.
Which is just the definition of a half moon (technically called a quarter moon). Which is why it's really weird to be asking "what if a full moon were at 90⁰ from you compared to the sun?"