Crap. I see it on Linux as well. Why do people always seem to find stuff immediately after I tag the source for a new release?
Although the opf and toc will flip in the Book Browser if one of them is highlighted when creating the index, that's just cosmetic. The elements that are being reordered in the spine seems to be limited to those items that are also guide elements (semantics).
EDIT: I see that Doitsu also figured out the Guide connection.