Re: what "FOI is for" please see my comment above, excerpting FREEDOM OF INFORMATION IN FRANCE, LAW AND PRACTICE.

Re: "Weird" documents: The CADA and courts have routinely recognized that documents in formats such as audio recordings, x-rays, photographs (of submerged shipwrecks, no less), video, application source code, and computer algorithms may be considered administrative documents, communicable to the public. FWIW, a 3D scan being an administrative document doesn't seem weird at all to me, nor did it seem weird to the many government attorneys at the CADA analyzing the issue, nor to the cultural heritage and open source and digital rights experts and advocates who joined my case, nor to the Paris court.

The Conseil d'Etat did not even say that scans could not be administrative documents, or that that would be weird; they just ruled that these documents in particular were akin to physical works and therefore part of the museum's inalienable collection, and so were outside FOI law.