I have no idea :-). Frankly I was under the impression that this requirement had been weakened/removed over the years, but this is what they write on the official website and I cannot find any reference about that so that's why I wrote "how/if it works in practice"

(maybe the devil is in the referenced details, but alas I have not time to investigate now)

But my point was more about the matter of principle: it is reasonable for the government to ask a copy of the works (for preservation reasons) in exchange for time-limited rights over it.