The Almighty also says that Cultivation is better at seeing the future than he, which fits well with the idea of "cultivating" people for their destinies. Perhaps Cultivation can see someone's future and provides them with a curse that nurtures that future purpose.
Also, the Nightwatcher is referred to as female and Cultivation is described by The Almighty as "she."
Lastly, the tale that Szeth hears of someone stealing a sphere that glows black at night from the Nightwatcher sounds distinctly.... Shard-y to me.