That's actually a valid choice in an extremely watt-hour per day (or week, or month) constrained environment. Like a relatively small to mid sized sailboat crossing a whole ocean. If you have very limited solar power, for instance, and you have critical instruments/radios and stuff to power.

If you have a "house power" 12V battery bank, and a regular laptop which expects 110-240VAC input, 19VDC output (example, random Dell) power brick which is being fed from a small true sine wave inverter, like 12VDC-to-120VAC, you're losing energy to heat and the DC to AC conversion process.

You're converting DC to AC and then the laptop is converting that back into DC. Ideally you do something like wire up a small inline fuse and a tiny meanwell DC-DC converter that can take 12VDC input and output 19VDC natively.

He has basically replicated on a limited budget and in a very small space on land a setup that is not that different than economically built DC power systems are done on boats.