Lets start a debate...
If you swap out a CU in a house, it's accepted it will be a dual split or RCBO type, offering 30mA protection to all circuits (exceptions here and there).
In a commercial, where do you stop?
For example, an existing 8 way TPN DB is fully loaded, having 24 single phase circuits, half a dozen with RCBO protection, as feeding sockets. You need to add more circuits. You could add a second 8 way DB adjacent, giving you another 24 single phase ways, and use these for your new circuits.
Or...
You could swap out the DB, because it was obsolete, damaged, or you just wanted one neat enclosure, with a 16 way TPN type, doubling you're capacity. Would you be obliged to install 30mA protection to every circuit where cables are buried in a wall? In many commercial installs, this could be all circuits....
If you swap out a CU in a house, it's accepted it will be a dual split or RCBO type, offering 30mA protection to all circuits (exceptions here and there).
In a commercial, where do you stop?
For example, an existing 8 way TPN DB is fully loaded, having 24 single phase circuits, half a dozen with RCBO protection, as feeding sockets. You need to add more circuits. You could add a second 8 way DB adjacent, giving you another 24 single phase ways, and use these for your new circuits.
Or...
You could swap out the DB, because it was obsolete, damaged, or you just wanted one neat enclosure, with a 16 way TPN type, doubling you're capacity. Would you be obliged to install 30mA protection to every circuit where cables are buried in a wall? In many commercial installs, this could be all circuits....