But usually a van physically transports the book to the lendee...

I think the debate will be if making a digital copy and locking the original book in a safe is equivalent, and if I were a judge, I would say "no", because to say otherwise significantly weakens copyright in so many other ways.

It seems like "faster vans" and "more effective nagging people to immediately return books they have already finished" would also weaken copyright under that line of argument; both allow you to loan the same copy to more people in sequence.