From what I understand, to work with copyrighted books they need to essentially format shift (i.e., scan and destroy the physical book). So a book vault would not solve this issue.

A book vault would still be useful for out-of-copyright works, but this would only cover a (probably relatively small) portion. Also, I'm not sure how easy it is to reliably determine copyright at scale, so they might just decide that it's not worth it.

At this point my only hope is that in the long run these scans make it to the public somehow (leaks, copyright changes/expiration, whatever), where they can then be accessed and preserved by everybody. Then we could have our true digital library of Alexandria.