If we are to class voluntary standards as legally mandatory then yes I would agree, but they aren't.
The way it was explained to me by an local authority fire inspector during a Fire and Rescue fire safety inspection of a care home was;
Safety Signs & Signals Regulations 1996 - lays out what you must do in law (mandatory) - the Reg's state that the signs shown in Schedule 1 of the Regulations are to be used when it is necessary to convey the relevant message(s) or information that is required, and signage should be easily understood by anyone in the area leaving no ambiguity. Signage is prescribed in the regulations for dimensions for the distances that they are to be viewed from, colours, and percentages of colours.
British Standards \ EN Standards - are guidance and advice only with no legal requirement to take as entirely prescriptive, but to aid\assist in meeting compliance to the Regulations where it is necessary.
So when the topic of directional arrows came up above final exit doors on the fire safety inspection, the local authority fire & rescue inspector stated that directional arrows are not mandatory above final exit doors because there is no ambiguity as to where you need to go to exit the building, as the final exit door is right in front of you, and directional arrows were only required when a change of direction occurred on the escape route to maintain the (easily understandable to anyone in the area leaving no ambiguity as to where to go to exit the building) aspect.
Very similar to fire extinguishers, where chrome bodied units are becoming popular. British Standards say the extinguisher body shall be red with the appropriate 5 to 10% colour identification band relating to the contents, And that the markings on the extinguisher shall be contrasting colours to the background. Same again, the enforcing authority in my experience does not compel businesses to remove these and replace with red bodied units because British Standards are guidance only and that the extinguishers still comply with the easily identifiable criteria.
I am not saying British Standards should not be followed, just that they are not prescriptively mandatory as so often gets stated, that's the regulations domain, and if you can satisfy the regulations requirement through another method, then that is often sufficient (depending on the aspect concerned and the technicalities of it of course).