The obligation to display the warning signal does not apply to "information or status displays" as defined in the regulation. Any display which is more than an "information or status display" should show an appropriate message that takes into account the capabilities of that display.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.