The museum's own internal request for clarification said they are administrative documents.

  ...According to the advice of February 7, 2019 issued by the Commission d'accès aux documents administratifs (CADA)1, engaged by you, the files in question would constitute communicable administrative documents, insofar as they are developed and held by the Rodin Museum as part of its public service mission. In addition, CADA rejected various arguments in favor of of their non-communicability2. It also indicates that these documents are reusable, including commercially, but that the museum can establish a pricing for the reuse of its three-dimensional scans.

Re: "FOI is for":

From FREEDOM OF INFORMATION IN FRANCE, LAW AND PRACTICE, Dr. Yseult Marique (Essex/Speyer), Dr. Emmanuel Slautsky (Université libre de Bruxelles) https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3033917

Page 19: "Before 2005 the reuse for commercial purposes of documents disclosed under the FOIA was restricted. Since 2005 and the implementation of Directive 2003/98/EC a right to reuse public information contained in administrative documents for purposes other than those for which the documents were initially prepared or received by the authority has been established under the conditions currently set out in book III of the CRPA. This right to reuse is made more effective by the fact that, whenever public information is electronically disclosed, it must be disclosed in an open standard that can easily be reused and automatically processed. This is important as inadequate standards significantly limit the possibilities for reusing administrative documents … The reuse of public information is normally free of charge. This principle is one of the main measures adopted in recent years in France to encourage the reuse of public information as part of the French policy of open data within the public sector. Public bodies are therefore compelled to allow economic operators to reuse valuable data generated in the public sector freely."

Page 39: "The FOIA has failed to trigger a revolution in how citizens request access to administrative documents. There is a fair number of requests. Sometimes these requests touch highly sensistive political matters (e.g. access to financial information related to President Sarkozy’s electoral campaing, Areva’s security failure etc.). However, all in all, the FOIA seems to be only used in marginal cases. The FDRA sought to bring a deep shake-up here. It sought to develop a stronger market logic with a clear demand-side and a clear offer-side to administrative data and documents. The pioneering idea that France seeks to put forward is that administrative information is economically valuable and that putting this information on the web will spur actors to use it, analyse it, dig into databases and eventually make valuable use of this newly acquired knowledge (i.e. because of economic uses or thanks to calling public bodies into account)."

What is the source of your knowledge of French FOI law? Are you already familiar with this topic?

Have you ever read this? https://eur-lex.europa.eu/eli/dir/2019/1024/oj/eng

I hope La Quadrature and company appeal this refusal to the EU.

Also even without the context above, a museum preventing people from experiencing and studying items from its collection (since the point clouds were apparently ruled such) is enough of a grounds for activist action against them.

Absolutely. An “activist” wasting time and money of museums (and probably taxpayers) worldwide due to a misleading interpretation of FOI.