The IET/BSi regulations are not retrospective. But today any new socket output or cable at less than 50 mm below surface needs RCD protection at 30 mA, and in many cases manufacturers stipulate the type of RCD often type A or better is required.
The RCD FCU has been a god send to comply with regulations, however the BS EN number for a RCD FCU is often not the one the BS7671 regulations stipulate, so technically still not compliant.
As to if it really matters is another question, my house is all type AC curve B RCBO protected, with a TN-C-S supply, to comply to the letter of BS7671:2018 since I have an inverter washing machine, and inverter fridge/freezer and inverter freezer, and an induction cooker plus all LED lighting it is likely to comply to the letter I need type A curve B RCBO's.
However I have done a risk assessment and I feel with 14 RCBO's the chance one is frozen due to DC at the same time there is a fault is very slim, so I am keeping the type AC RCBO's, if it had been a TT supply maybe I would have felt different, but it is a TN supply so not relying on the RCD part of the RCBO.
However much we would like to simply follow rules, in real terms it is down to a risk assessment. And when my son at 14 years old in the last house passed his RAE (radio amateurs exam) I knowing what radio amateurs do, felt very proud of my son, but also felt RCD protection of all circuits was required. Well before RCD protection was required is fitted them
but still using rather old Wylex fuse boxes with the fuses swapped for MCB's. I think this was around 1992 well before the consumer unit with RCD's built in.
This house with all RCBO I have had one or two trip when the roof leaked and the sockets and light switches got wet, but with 14 RCBO's it did not really cause a problem, again risk assessment, I decided it was worth the extra £200 approx to have all RCBO's rather than twin RCD's. Mainly due to cost if the freezer fails, I lost two freezers full of food in the last house, which cost me well over £200, so I considered worth the extra.
But 1978 when my previous house was built there was not requirement for RCD protection with a TN supply, not sure of the date when the ELCB-v came in for TT supplies, or when it was outlawed and the ELCB-c (RCCD or RCD) replaced it, but in the main only 100 mA anyway, the 30 mA was to start with only for outdoor supplies, it was around 2008 before it was required for nearly all sockets.
But there is no question
Emma Shaw would be still alive today had in 2006 RCD had been required. OK her death was not blamed on lack of RCD protection, but it would have prevented her death. There was also a MP's daughter, but although clearly no want wanted the deaths, they were rare.
I have not read any reports of death in resent years, which points to the RCD stopping them, but there is still nothing forcing one to upgrade, that is up to you.