That's so delightful that he's enjoying it, and I kind of love that willow/Tara is his favourite pairing. They were my faves too but I'm also very fond of Buffy/Angel and willow/Oz. I think it's just fascinating to see someone watch it who doesn't instinctively know the tv tropes of the time (like year round episodes and timing of shows) and has vastly different expectations for queer storylines -- and possibly for female led action shows. That was a huge thing at the time but it's hard to remember how surprising it was for a genre/action show to be so popular with a female lead because it's common now.

As for Xanders Lie, I remember forgiving Cancer for it but also being terribly justified that it got thrown around in s7. For any flaws it might have had, I still think BtVS had great character continuity. It knew it's characters and it let them grow.