New kitchen does it need own fusebox or change just the mains fusebox?

[ipf]

Devil might be in the details, it should at least identify the fact there is more than one DB (CU) now, though all that really matters is the new circuits were properly designed and implemented (i.e. tested)

Something tells me that things could well be well in order. It's sometimes all about being able to interpret information given. As previously advised, it's no doubt the best way forward to get a full explanation from the person who best knows......the installer.......rather that tie yourself in knots.
If not happy, get someone else qualified to take a look.