So... not understanding a continuity in which Lupin/Tonks would be alive and knowing specifics of horcruxes, other than the night/day of the final battle.
Author's response
wjwarren4269 -- yes, that's more or less right in terms of when the chapters are set -- she was taken two days before the battle, unless I got the dates wrong.
Also for the purposes of this story, I'm using the premise that trusted order members were getting much more information than Harry all along. So revelations at the final battle for Harry in the original timeline would not have been, in my universe here, necessarily revelations for Tonks.
I have no actual commitment to canon, although I try not to depart from it by accident. :) I'll go back and clarify things if this story becomes popular enough that I both get lots of reviews and lots of confused people. (I do not expect this to happen.)
(This is my first attempt at using the "respond" function. Let's see what it does!)