code: private boolean isValidWeakMetaClass(MetaClass metaClass, MetaClassRegistry.MetaClassCreationHandle mccHandle) {
          if(metaClass==null) return false;
          boolean enableGloballyOn = (mccHandle instanceof ExpandoMetaClassCreationHandle);
          boolean cachedAnswerIsEMC = (metaClass instanceof ExpandoMetaClass);
          return (!enableGloballyOn || cachedAnswerIsEMC);
      }
docs: if EMC.enableGlobally() is OFF, return whatever the cached answer is.
  but if EMC.enableGlobally() is ON and the cached answer is not an EMC, come up with a fresh answer