code: protected void checkRegisteredDataUsingReservedWord(ActionRuntime runtime, WebContext context, String varKey) {
          if (isSuppressRegisteredDataUsingReservedWordCheck()) {
              return;
          }
          if (context.getVariableNames().contains(varKey)) {
              throwThymeleafRegisteredDataUsingReservedWordException(runtime, context, varKey);
          }
      }
docs: Thymeleaf's reserved words are already checked in Thymeleaf process so no check them here