Yes, when I saw this theory, I did think of the moon that fell. In Rosharan culture, the moons are each important - and there are three of them.
However, if one fell, that means that there are former in total, throwing of the theme of three, ya know? So maybe the one that fell was replaced by one to represent the Nightwatcher - or perhaps the sibling.
Silly theory, can and will accept criticism.