src/tools/disks/zfs.rs: add comment

src/tools/disks/zfs.rs

@@ -209,6 +209,9 @@ pub fn zpool_list(pool: Option<String>, verbose: bool) -> Result<Vec<ZFSPoolStat
     let mut command = std::process::Command::new("zpool");
     command.args(&["list", "-H", "-p", "-P"]);
 
+    // Note: We do not use -o to define output properties, because zpool command ignores
+    // that completely for special vdevs and devices
+
     if verbose { command.arg("-v"); }
 
     if let Some(pool) = pool { command.arg(pool); }