Actually the announcement doesn't "prove it cannot actually handle any load".
It simply mentions that the batteries can be connected serially and the voltages add as expected. And that the voltage generated is proportional to the ambient humidity.
That's as far as it goes. The rest is your own conjecture.
Its not intended to power LEDs or cars or mining equipment.
IMO the intended development is to miniaturise the cells and then connect them into packs that might power wearable printed sensors and memory chips for data recording. Cmos circuits for instance can be very low loads and may require only a few nanoamps...
