Yes boys and girls, you REALLY need to carry a spare...

Vehicle would have to be super heavy, like really overloaded to bend the frame by jacking one corner up only. However the leveling jack will cr@p out long before you could put enough pressure to permanently deform the truck frame.
Lifting one side or one and with 2 jacks simultaneously is to protect the jacks, not the vehicle and it's a good, almost necessary practice with RV jacks.