There's a lot of that with this guy... His comment about requiring a low power environment so he discards all laptop power bricks. Dude, unless you're powering things off a hand cranked dynamo a few laptops are not going to melt your fuse board.

My guess is that the "why" is largely just showing off, coupled with oddness.

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.

His logic is correct though. The native power of his grid is 12V. He has a 20V step-up circuit and an inverter. 12V -> Inverter -> 12V is only good for UPS. He can directly setup USB-PD up to 9V from the 12V circuit or full 12V PD from the 20V one.

Also, I believe he hoards the power bricks as he notes.

What he does is not ideal, and I don't share the same view with him, but I understand what he does.

It is odd but also fascinating. If he likes it that way then all the power to him. He's not exactly trying to convince others to do the same.