Umm. That part was foreshadowed and fitted within the larger story.
The first time they glitched together, perhaps. Them staying connected and giving Harry a perfect defence in the next book? a total asspull (and that after a number of books where Rowling made every detail count, making it that much more jarring)

Sure, it's a saga of how they died. However, is it something we, the audience needed to know? I don't think so. It just seems like padding, for padding's sake.
A matter of personal taste. There is no story you actually need to know.