I believe that in the context of copyright, 'exact' doesn't mean a 100% perfect copy. If I make a film, I hold the copyright for it whether its distributed on VHS, DVD, or online streaming, even if the quality on VHS is different than the film shown in theaters. It'd be like if changing an image from jpeg to tif changed its copyright status. Your example elsewhere of correcting a few typos and saying it's a different work is similar: it's still the same work, even with the minor tweaks.

Anyways, copyright is weird and complicated and there are many people who don't really understand it. But your theory that archive.org is going to get a copyright on everything they scan and store is not rooted in any sort of legal reality.