Eh, I just assumed it was garden variety late 90s Christ imagery. No greater love has a man than this, that a man hath laid down his life to save to his friends, and to conquer death, and preferably put your arms at a 45 degree angle at some point. The core symbolism with, well, Kore, is that her release represents the end of winter, and her bondage represents the end of summer. There’s no self sacrifice, Kore was raped, in the older use of the word, of course, and Demeter abandoned her responsibilities, and Zeus condoned the whole thing until the Earth was plunged into chaos. Oh, and surprise, eating pomegranate seeds binds gods to hell, which seems like the oddest piece of god related trivia in the whole of Indo-European religion. In any case, it seems more like Demeter's issue, not her daughters. And the main issue is, Buffy saves peoples. Kore does not save Hades, if anything, she becomes tainted by the Underworld, never has children, and her mother’s mourning never diminisheds. Buffy saved both Angel and Spike, literally from hell. If anything, she is more like Orpheus (more Faith's thing) or Heracles, both of whom bent Hades to their will.
Of course, now I kind of want to see the episode where Lord Sweet returns from the special hell for the cast of Glee, to take Dawn or Xander as his bride in his chariot, and Buffy has to get them back. See, why couldn’t the comics show stuff like that? “Nine trillion four billion five million ten thousand minutes, that’s how long you’ve been down here.”