On the contrary, with my factory steps, they are indeed independent from each side. (Driver open, step deployed...passenger remains in home position. And vice versa. Cargo lights and both puddle lights do come on though in each scenario.
So maybe there’s another power source to tap other than cargo to achieve this goal. But as others have said, tapping each running board might not be a constant power source. And as you mentioned earlier, to just tap everything on driver side cargo, this seems to be easiest.