If CASA were capable of pragmatism, instructors could instruct for any skill that they themselves have demonstrated.
This was the case for quite a few things under CAR 5. The Part 61 regs have added a significant amount of cost to an instructor (or organisation) who'd like to or has to add training approvals to their rating. Whilst the 'new' instructor rating has stripped a bit of cost, it doesn't make up for the added approvals cost.