+2, but i think it's just how it's worded as i can tell what he's getting at..... on a 32A ring circuit for example, the mcb is protecting the cable from carrying more than 32A, and as the circuit is suppling 13A socket outlets whatever is plugged into that circuit has to be covered by a lower rated plugtop fuse.
However as the mcb's are more sensitive than the plugtop fuses they often operated before the plugtop fuse anyhow therefore offering some protection to the apliance.....and in the case of a lighting circuit the mcb's certainly offer protection, and an RCD is a totally different thing altogether detecting earth faults that no plugtop fuse will detect anyway