Having slots in the flash hider, making it some what functional, would turn it into a "military style semi automatic" under our laws - making it illegal to own without an endorsement on your firearms license, a permit to procure for the rifle, and a 6mm steel gun safe to store it in. I could however drill holes in the flash hider, to turn it into a muzzle break, or pull it off and put a suppressor on, and it would still be perfectly legal to own on a standard license. And putting it in a locked cup board would be sufficient under our arms act.
The creators of NZ and Canuck gun laws share a similar base of intelligence