@CBE
Replacing a consumer unit in an existing installation is an alteration to an existing installation, not a new installation.
Look at the model EIC on page 510
There is a box for comments on existing installation, it says “in the case of an addition or alteration see Regulation 644.1.2”.
Regulation 644.1.2 For an addition and/or alteration to an existing installation, any defect or omission that will affect the safety of the addition or alteration that is revealed during inspection and testing shall be corrected before the Certificate is issued.
For example, earthing and main bonding needs to be suitable and upgraded if required to ensure ADS in the event of a fault with the circuit protection in the new consumer unit operating correctly.
You are confusing the requirements with those in the preceding Regulation 644.1.1 which doesn’t allow any errors or defects to be recorded on the certificate for new installations.