Yes, the term 3/4 ton etc is antiquated now and for maybe 50+ years and is a general identifier for pickup trucks etc segments. So is 1/2 ton and 1 ton. The carry weight term is really referring to the truck's chassis, frame structure, and load carrying ability/capability as was manufactured as an OEM vehicle. does not refer to proper alterations or upfitting done to said vehicle after OEM build.
Such as for Ford or GM various pickup truck segments in past years:
1/2 ton = about up to 2000 lbs cargo max for a vehicle configuration within the segment. Many "1/2 ton" trucks were manufactured as stretched out (crew cab etc with a long bed) versions built on the 3/4 ton truck segment frames but still marketed as 1/2 ton trucks.
3/4 ton with it's stronger frame/larger engine and and/or heavier driveline options etc = up to about 3000 lbs max cargo for a vehicle configuration within the segment.
1 ton SRW = up to about 3500 lbs max cargo for a vehicle configuration within the segment.
1 ton DRW = up to about 5000 lbs max cargo for a vehicle configuration within the segment. The two extra rear wheels and higher capacity springs are the main reason for the higher cargo capacity. Now Ford has up to about 6900 lbe capacity and the 2015 GM's have up to about 7400 lbs capacity available. A far cry from the 5000 lbs of yester year!
Cab configuration/size and length of frame plus added weight of options included along with engine/driveline capability and GVWR brake capability (stopping ability) lowers load carrying capacity for a vehicle of each "size" segment.
There's NOT a black and white number for load carrying, towing, etc for any of the segments because of the vast configurations, options, and engine/drive line choices available.
Other pickup manufacturers generally had somewhat of the same type of segment classifications but usually had lower load carrying capacities (GVWR) thruout the individual segment classifications they offered due to chassis/frame structure design and/or driveline capabilities and/or braking capability at max GVWR. There is and never was a black and white line defining the limits of each "size" segment in the automotive industry.