Given how well these two know each other, they're both clueless. We might need a real life or death situation to get them to really open up. And on the subject of Spike's soul, how can Buffy not know why Spike would think it's a game changer. After everything she said about souless, evil demons. Super chappie.

Why is Spike so sure the soul matters?  Well duh -- after all the years of banging on about it, I'm hardly surprised he does.  At least they're talking ...  a bit.

So, Spike still has his defensive walls up. Hardly surprising since Buffy was only able to vocalise her feelings once he had the soul.
She's also a little more ambivalent than she'd admit. 
More please...