It is a <i>file</i> system, consisting of file system objects, like files and directories.<p>Already exposing processes as files is an abstraction. It somewhat works because you can imagine the file representation being maintained by the process. But it is an abstraction, because a process <i>is not</i> a file.<p>But what is more important: A file system is a <i>hierarchy</i>. At the root is the most fundamental object. Each level has <i>subordinate</i> objects. That the model you expect.<p>Having UEFI variables mounted as a file is a surprising loop back to something even more fundamental that the OS itself: The firmware of the physical computer. It a breach of the mental model.<p>It breaks one of the most fundamental principles that should be followed in man-machine interaction: The principle of least surprise.<p>I have a machine. I have installed an operating system on it. The OS manages several disks. On the disks the OS manages file systems. I expect the files of that system to be managed by the OS.<p>I <i>do not</i> expect that regular file system actions have effect <i>outside the hierarchy</i> of the directory on which I perform the actions. Specifically I <i>do not</i> expect files on that system to manage the physical computer.