One man's pedantry is another man's Wiring Regulations requirement for consumer units to be type tested assemblies if you want to take advantage of the conditional rating of <16kA devices as 16kA ones.
536.4.203 Integration of devices and components
The relevant part of the BS EN 61439 series shall be applied to the integration of mechanical and electrical devices and components, e.g. circuit-breakers, control devices, busbars into an empty enclosure or existing low voltage assembly. In low voltage assemblies to the BS EN 61439 series, e.g. consumer units, distribution boards,
incorporated devices and components shall only be those declared suitable according to the assembly manufacturer’s instructions or literature.
NOTE 1: The use of individual components complying with their respective product standard(s) does not indicate their compatibility when installed with other components in a low voltage switchgear and controlgear assembly.
NOTE 2: Incorporated components inside the assembly can be from different manufacturers. It is essential that all incorporated components should have had their compatibility for the final enclosed arrangements verified by the original manufacturer of the assembly and be assembled in accordance with their instructions e.g. the consumer unit, distribution board manufacturer. The original manufacturer is the organization that carried out the original design and the associated verification of the low voltage switchgear and controlgear assembly to the relevant part of the BS EN 61439 series. If an assembly deviates from its original manufacturer’s instructions, or includes components not included in the original verification, the person introducing the deviation becomes the original manufacturer with the corresponding obligations.
536.4.201 Fault current (short-circuit) ratings
The relevant fault current (short-circuit) rating of the assembly should be equal to or exceed the maximum prospective fault current at the point of connection to the system. The terminology used to define the short-circuit rating of an assembly is given in the BS EN 61439 series as follows:- rated short-time withstand current, Icw- rated peak withstand current, Ipk- rated conditional short-circuit current, Icc.
The assembly manufacturer’s ratings and instructions shall be taken into account.
For an installation with a 230V single-phase supply rated up to 100A that is under the control of ordinary persons, switchgear and controlgear assemblies shall either comply with BS EN 61439-3 having a suitable fault current (short-circuit) rating for the maximum prospective fault current at the point of connection to the system or
be a consumer unit incorporating components and protective devices specified by the manufacturer complying with BS EN 61439-3, including the 16kA conditional short-circuit test described in Annex ZB of the standard.
NOTE: When the single-phase PSCC value of 19.6 kA is cited from Engineering Recommendation P25, the 16 kA conditional rating described in Annex ZB of BS EN 61439-3, for incoming service equipment, will satisfy design requirements where the service cable is at least 2 metres in length.
I have highlighted the parts which require compliance with Manufacturer’s Instructions.
Re BS EN 60439-3 Annex ZB:
BEAMA Technical Bulletin - Consumer Unit 16 kA Conditional Rating Application