So far as I am aware, the moon was considered in early India, as in many other civilizations,
to be a bright body, not a source of reflected light. So it is unlikely that reflection plays
any role in the mind-moon analogy.

I would suggest, however, that serious thought be given to the phenomena of waxing and waning.
Indeed, the increase of wisdom (prajñā) is not infrequently compared in Buddhist texts to the
waxing moon.

Unlike the sun, which blazes quite constantly, the mind strengthens or weakens, both periodically
and in the course of life -- if there is metaphor that links mind and moon, I suspect that it is
to be found here.