ReverseFlight,
Slight misunderstanding there: In the US it is a prerequisite for all grades of aeroplane flight instructor to hold an IR. No ifs or buts. Doesn't matter if the instructor rating does or does not authorise instrument rating training. BTW, lots people hold 'just' a CFI without holding CFI Instrument or Multi Engine Instructor ratings although many move 'up' and add the other two instructor ratings too.
It's a little different in Oz. The CASA prerequisite is for the instructor to have Night VFR privileges no matter which level of instructor rating s/he holds. NVFR privileges can be achieved in two ways: By holding a NVFR rating or by meeting the NVFR experience requirements specified for a Command Instrument Rating. Similarly to the US, many instructors hold 'just' a Grade 3 but also many move 'up' to Grade 2 and/or add multi instructor. Some even add Instrument Rating instruction to their Gr.2. Fewer move to Grade 1 though which automatically gives the equivalent of the US' CFI Instrument rating
As a side note for Oz, a disadvantage to using the 'NVFR under CIR' method is that NVFR privileges lapse when the CIR lapses whereas the NVFR rating is permanently valid.