I understand what the "Rated capacities" say, but the ST tires have no reserve capacity whatsoever. The LT tires do have substantial reserve capacity.
Please don’t take this as a flippant remark.
Your remark is a presumption. The facts are printed on each tire’s sidewall and certified. Any tire manufacturer that would say otherwise would be misrepresenting their own product. Vehicle manufacturers must rely upon tire manufacturers to provide them with tires that will fit the needs of their vehicle’s. There is no room for misinformation.
Most of us are most familiar with the needs of our everyday vehicles (Autos, PU trucks, SUVs etc…). The DOT mandates that a certain amount of reserve tire load capacity be provided in the OE tires for those vehicles. It is provided with tires designed for that particular service and includes the manipulation of tire pressures to achieve the necessary load capacity reserves. That same type of mandate is not required for tires on RV trailer axles, thus the (sometimes) misconception.