The motivation to write this plugin is given by the two paths that exist in /etc/fstab: the device file and the mountpoint. A missing file is not necessarily an error, because the device file may appear later when a device is plugged in and the mountpoint may be there when another subsequent mount was executed. So only warnings are yielded in that case. One situation, however, presents an error: Only an absolute path is allowed to occur for both device and mount point. When checking for relative files, it is not enough to look at the first character if it is a /, because remote file systems and some special names are valid, too.
If the meta key check/path is present, it is checked if the value is a valid absolute filesystem path. If a metavalue is present, an additional check will be done if it is a directory or device file.