I have to say that I'm a little surprised that the BnF supports a framework that facilitates original image downloads and bills itself as "breaking down silos". They're kinda famous for charging fees for access and and putting restrictions on using public domain works that have already been digitized. (see e.g. the "Provision of an image already digitised" section of https://www.bnf.fr/en/reproduction-products-and-fees#bnf-ima...)