Potatoes are absurdly good at this.
You basically can’t over eat boiled / baked potatoes.
https://optimisingnutrition.com/calculating-satiety/amp/
I tried this with sweet potatoes once. Best I ever felt. Super boring.
They need to increase salt because they were losing salt thus water, it's what happens when you cut all processed food. Even the added salt is still much lower than what you'd ingest in a normal SAD diet.
On a ketogenic diet (which is more extreme that this, but to prove my point) the best solution not to feel crap the first few weeks is putting a little salt in your water. Whenever you feel a little weak, have a little salt. Works fantastically, then about a month in your body learns to retain the smaller amount of sodium better, so you don't pee as much nor need to supplement any salt.
This diet specifically did the opposite of this "advice". Potatoes are pretty high up on the complex carbs list and one of the takeaways in the article was a finding that some people needed to increase salt consumption in this diet. Their figures also showed a linear relationship in weight loss over time that seems, at least with four weeks of data, to much more sustainable than many other diets and suggests what was lost wasn't just "water weight".
In general a lot of the article is about how much this diet is about ignoring usual experienced/serial dieter "advice".
This article was definitely clickbait to get a lot of people asking these questions about what about this diet makes it "remarkable", especially because it ignores so much "experienced" dieter advice. The working theory is that it may lower a person's lipostat, but that's just a working theory and the article acknowledges it will be a few months of follow ups to best evaluate that working theory.
An article can be both clickbait and thoughtful discussion.