BS7273 part 4 includes the recommendation that failure of the addressable data reaching the fire alarm interface device should also cause it to fail-safe.
Most addressable protocols which are available, and have been available for years, cannot achieve this. There may be a few that can, but the manufacturers of these don't seem to be trumpeting this feature as a unique selling point, so I wonder if there are other issues which make it unwise for them to advertise 'can meet all the recommendations of BS4737-4'.
I'm sure that when fire panel/accessory manufacturers deem it cost-effective to include the possibility of meeting all recommendations of BS7273-4 they will probably include it.
Maybe their current apparent lack of enthusiasm for this feature is because they believe this particular recommendation to be a 'fail-safe to far' and without particular merit for the cost it would take to achieve.
It would seem that they can get their products through Third Party Certification because this feature is not considered an absolute necessity for a fire alarm panel used in most systems but only necessary for those which will definitely be used in a system which also has a BS7273-4 electromagnetic lock system installed.