Building regulations can only be applied to new buildings or material alterations whilst they are being built, can you imagine the cost of bringing Windsor castle up to date?
You won’t get certification to say it meets the regulations. Once a building is built and handed over, building regulations are out of the window except for material alterations.
The fire safety order then comes onto force which (amongst other things) requires the responsible person (or their agent) to conduct a fire risk assessment on the building and address the findings. It is not a money-making scheme,
If the glazing says it is fire rated, then unless the assessor can prove it isn’t then it’s acceptable