They won't destroy the books very likely but also the amount of capacity and money to do this on a huge scale is (as far as I know) totally unprecedented.
And it's irreversible when the books are really destroyed.
That combination makes it an urgent and important issue.
Libraries have been trying to do exactly this (digitising) for many years, without funding. Imagine the wealth of human knowledge that might be in proprietary llms after this? Will there be a path back to the source material? I hold out hope that this digitisation effort will preserve the digitised source materials in the public domain somewhere