>I've seen other websites archived in this manner.

Futaba is not phpbb/vbulletin nor a gallery. Not only do old threads get deleted, but any attempt to archive the contents would be filled with duplicate images. On top of that, in the years since it started an archive would have likely grown into the terabyte range. It's a constant stream of images and posts. Just what kind of archive were you expecting?

Now a 2channel model kit board archive, that you might be able to find.