"if you have a Class C license which is essentially a car license, then you’re clear to drive tractors on any road in Australia - even ones TOWING IMPLEMENTS."

"The licence allows the holder to drive cars, utilities, vans, some light trucks, car-based motor tricycles, tractors and IMPLEMENTS SUCH AS GRADERS, vehicles that seat up to 12 adults, including the driver."

I think "GRADER" here could be misleading, for the first thing that might come to mind might be an motor grader (niveleuse). In the agricultural context which is that of tractors, a grader can be an attachment (blade) at the back of a tractor fufilling much the same purpose as a motor grader, as here:
https://farmgard.com.au/product/agricultural/

So I think it is safe to assume they mean 'agricultural implement', i.e. something towed by a tractor (Russian tanks don't count because they have their own engines).

"AGRICULTURAL IMPLEMENT A vehicle WITHOUT ITS OWN AUTOMOTIVE POWER, built to perform agricultural tasks, and includes an agricultural trailer. [...]
"Agricultural vehicle An AGRICULTURAL IMPLEMENT or agricultural machine."
[From the glossary of the Australia's National Heavy Vehicle Regulator]

"An AGRICULTURAL IMPLEMENT is an agricultural vehicle WITHOUT ITS OWN AUTOMOTIVE POWER, built to perform agricultural tasks and includes agricultural trailers. Other examples of agricultural implements include augers, conveyors, seeders, planters, rakes, tillers or irrigating equipment."
https://www.vicroads.vic.gov.au/business-and-industry/heavy-...