US Experimental aircraft include homebuilt aircraft like Vans, Rutan etc designs.
Here those are VH registered and included on the CASA register.
But the gyrocopters, hang-gliders, ultralights etc here counted in the BITRE numbers are not counted in the FAA numbers - and there are a mighty lot of such aircraft here.
BUT the point remains:
Providing a MORE EFFICIENT SERVICE means fewer people / less cost than a less efficient service.
The argument here is not about comparable statistics but about the provision of a safe separation service to aircraft who are unable to separate themselves.
US ATC separates all aircraft in IMC. Australia does not.