Interestingly, another David Brin novel was nominated for the Hugo in 1996 (_Brightness Reef_, one of his Uplift books).
I am not sure I belive the story about thr manuscript however. It surfaced just as the Internet was becoming a thing. Coincidence?
And I don’t see why the Internet is relevant: not everything that happened since the mid-1980s are internet-related conspiracies.
I was very glad to re-read it when:
https://www.usni.org/press/books/20000-leagues-under-sea
was published.
https://janbecke.com/portfolio-item/paris/
Take from that what you will.
Here's a site - ignore the warnings about the certificate - showing some of these images: https://jv.gilead.org.il/evans/illustr/