I just find it reductive to reduce everything to binary oppositions. Xander is always going to be straight man and Willow is always going to be a straight woman. I don't think that means that the dynamic between them will always be defined by that. Xander has had to make some pretty damning admissions lately, and so he abandons the highly gendered discourse he has been using since "Entropy."
I also wonder at the insane/sane dichotomy. Is Xander's profession of unconditional love rational or sane? He has used decidedly rational arguments to condemn Anya and Buffy, though these arguments have mostly been a mask to hide his angry at their perceived betrayal.
I think the scene at the bluff is a redemptive moment for Xander as well as Willow, which shows that there is a love between them that existed before and after the erotic/gendered fling they had in high school.
As mentioned, you can read up on my citations in further detail to understand the material I put forward a little better which all defend my ascertations:
Wilts, Alissa 2009, 'Evil, Skanky, and Kinda gay' Buffy Goes Dark, pp. 41-56
Bartlem, Edwina 2003, 'Coming out on a mouth of hell' Refractory: A Journal of Entertainment Media,
Booth, Stephen 2005, 'The Death of Tara, the fall of Willow, and the Dead/Evil Lesbian Cliche FAQ'
Faderman, Lillian, ed. 1994, 'Chloe Plus Olivia: An anthology of lesbian literature from the seventeenth Century to the present'
Foucault, Michel 1989, 'What is an author?'
Inness, Sherrie A. 1997, 'The Lesbian Menace: Ideology, Identity, and the representation of lesbian life'
Bercovitch, Sacvan 1986 'The Problem of Ideology in American Literary History'
Let me know if you have any issues getting hold of them and I can always pdf and shoot them through in an email to you. I'd love to discuss it more, but as you can imagine trying to summarise all of the information within the texts that reach the same conclusion as me would be way too exhausting!