The advantage to this setup, is that the inverter is shut off except when needed.
Without doing this mod, the thermostat circuit draws 120v continuously, preventing the inverter from dropping down into standby mode (and a cheap inverter might not even have a standby mode).
Thus, the only actual power savings, is whatever the inverter itself consumes while switched on. The fridge itself doesn't consume any less power (well...the led light does, but not enough to matter).
According to this...
https://www.amazon.com/BESTEK-1000W...01-20&linkId=052b882f0750258d2b4d9a712420ef61
...the inverter itself draws .6 - .8 amps per hour, so that would be 15 - 20 amp*hours per day in power savings.
So...um...kinda/sorta worth doing I guess. Depends. In a van getting most of its power from solar, 20ah/day would be a big deal. But then, just getting the 35ah/day to run the fridge with the mod might be a big deal.
As for doing the same mod to some other fridge, I suppose it could be done, but you'd have to study the schematic and guts of that fridge to figure out if it could be done, and exactly how to do it.
Doing it to a smaller fridge might not be worth bothering, the dorm size fridges are notoriously inefficient.
He mentions that the fridge he's using wouldn't benefit from extra insulation due to the way the compressor and coils are mounted. Using a different fridge, packed with extra insulation around it, and some low-power computer fans zip tied to the coils might save just as much power by reducing compressor run time.
Modding a chest-type (top loader) freezer, to run at a slightly higher temp so it can serve as a fridge, is a pretty common old school setup popular with the off-grid solar crowd because it's very power efficient.
The mod in the OP looks like a fun little hack, but despite the guy's anecdotal evidence, I wouldn't count on longevity. Especially using wirenuts.
And the doors need to be modded as well to keep them from popping open while under weigh.
He says 150 bucks, but that doesn't include the inverter, which is another 80. So figure 250. For that price, I'd rather add more solar, buy a small generator and a good battery charger, or just buy a 12v fridge.
