This lacks quite a lot of (interesting) detail. The differences between Windows and Ubuntu are more than the icons and the games; what about Office (OO is quite different, particularly for advanced uses of Excel), Outlook, Active Directory, NTLM authentication for internal (web)apps, .Net for in-house development, etc? These aren't all strictly speaking part of Windows, but they are part of the Windows ecosystem, particularly at large sites, and usually don't have Linux slot-in equivalents that are trivial to implement.

So, either the Gendarmerie Nationale didn't use any of those parts of the Windows ecosystem (which seems unlikely), or they made savings in spite of having to replace them (in which case the 'icons and games' remark is disingenuous), or they haven't accounted properly (which, this being a governmental entity, doesn't seem impossible.)