Why all those "too complex to analyze by data flow algorithm"

All these "method is too complex to analyze by data flow algorithm" warnings in v12.0.4 (and also earlier versions) is driving me crazy.

I am using the 64-bit version, on Windows 7.

For example this method:

   @Override
   public void cleanupInstance ()
   {
      try
      {
         JTree swingTree = watchesTree.getJTree();
         if (swingTree != null)
            swingTree.removeTreeWillExpandListener(watchesExpListener);

         tabPan.removeAllTabs();
         threadList.cleanupInstance();
         inspectorTabPan.removeAllTabs();
         executionPointContainer = null;

         autoInspectionSplit2.cleanupInstance();

         if (debugAdapter != null)
         {
            debugAdapter.cleanupInstance();
            debugAdapter = null;
         }

         if (scriptBeingExecuting != null)
         {
            scriptBeingExecuting.cleanupTempIpcFile(false);
            scriptBeingExecuting = null;
         }
      }
      finally
      {
         super.cleanupInstance();
      }
   }

What is so complex about it?