Interesting cuz I was thinking of Light/Normal load to be just the driver and a full tank of gas, and the Full/High load to be the maximum payload whatever it is for each model year, for my '16 its about 1488 Lb. And LR usually assumes the driver' weight to be 165 Lb (per their LR4 brochures).
And I am not quite sure if the 550 Lb tongue weight is really included in the maximum payload value of around 1488 Lb (lesser number if the truck is optioned up with more optional and production equipment if you want to maintain the total the Gross Vehicle Weight the same as standard equipped model).
Cuz if you take out 550 out of the 1488 Lb (1484 Lb incase of LR4), you are really left with only 938 Lb for all seven passengers with no luggage. Thats 134 Lb per passenger, doesn't make sense. So I am guessing that the 550 Lb of tongue weight has to be outside of the maximum payload.
Noticed that LR stopped mentioning Maximum Payload Weight value in their brochures starting from MY14 (SCV6 versions).
Tongue weight always comes out of payload numbers. You just touched on a problem that affects many cars. Maximum towing means less people hauling. This problem really affects crew cab 1/2 ton trucks.