I think the original question was about riding machines from from small to large..?.. here is how i would class them based on what i have seen and read about over the years early 60s-early 90s the "golden age" of garden tractors, riding tractors made before recycled chinese metal took over...
RER rear-engine rider mostly for mowing the grass, snapper and other brands with tiny wheels and small stamped metal "frames"
Lawn Tractor has small back wheels, no factory blade/blower (too flimsy) and just a tow ball on the back sheet metal "frame," for light "lawn carts" hauling leaves, mulch, etc.
Yard Tractor bigger than a lawn tractor and maybe a thicker frame. Limited factory options for front "snow blade" (thin metal) or even a small blower, still only a tow ball on the back. Armstrong lift.
Garden Tractor usually has 3 or more lug bolts on a rear flange hub. Rear rims usually 12-16." Factory ground implements like a heavy front dozer blade, factory rear option Cat 0 or sleeve hitch. Any rear PTO usually unique to the make/model. Can safely handle a small add-on loader, sometimes from the factory or dealer. Elec/hydro factory lift options from the 60s-on.
Super GT still "looks like a GT" just bigger and heavier but similar factory options. General consensus among the lucky owners which machines qualify in this category.
SCUT starting to "look like a small farm tractor." Should have a Cat 1 hitch from the factory, usually a "live PTO" that will handle things like a 4' field mower, etc. Higher pressure hydraulics than a GT can run a loader with no extra pump.
I don't know everything, just general observations, there are crossovers, like Snapper made a front snow blade for their RER and you could put a tow ball on but they'd wheelie easy and burn up the disc clutch on a hill. Some Ford YTs have rear flange hubs and big blowers from the factory. Some people still call a Farmall Cub or 8N a "garden tractor," etc. The newer big-box stuff just seems to get more flimsy with fewer implement options, weaker transaxles, vertical engines, etc. hence the "golden age" that many prefer, before parts were made in china from recycled beer cans and you could still fix things yourself with dealer spares...