The NSS and NTFS file systems on OES, NetWare, and Windows servers always control access to the files and folders they contain. Users seeking access through a file browser, such as Windows explorer, must generally have the required permissions on the file systems to gain access.
This is absolutely true when accessing files and folders through Filr. You cannot gain more access through Filr than the underlying file system allows.
Filr sharing is no exception. Shared access through Filr depends on the Net Folder proxy user having the required file system rights.