"My point about Spike's absence in the dream space is not that it's meant to conceal something. Just that it's distinctly odd that he's not there, and that his absence of itself could well turn out to be significant."

Oh I see it as being that Jeanty didn't want him in there (apparently he was partly responsible for what made the grade so to speak), and neither did Joss. They don't want endless reminders of how important he used to be in Buffy's life, and so after one 'bone' thrown to the fans in the form of that fantasy, that was it. They probaly thought that'll shut em up. *g*