It is way more interesting to figure out why would he say it. I think Buffy loved Spike not because she said it, but because this and her previous behavior, etc, for example.

I thought that too, about Buffy. I thought she'd loved him for a long time, in fact, but for the most part it only ever made things worse.

I completely agree about it being more interesting - the story gets way more compelling, to me, when you're dealing with lots of subjective viewpoints rather than the voice of The Author. And yes, much less depressing. :-)