How scalable the techniques are is one matter but I think the results speak for themselves in proving what's possible with careful (read: high labor input) management.
The way that desertification spreads is primarily because the soil has no capacity for holding water. The most common cause of death in deserts is not actually thirst but drowning. The inability to hold moisture means thatwhen there is rain it can turn into flash floods which will then wash away any top soil there already is.
There are countless techniques used by this group to target that specific problem and build soil safely that won't get washed away. As well as storing water in ways that won't lead to evaporation. They build swales and shape the landscape in order to manage how and where the water flows through the land and use windbreaks to resist the harsh winds that may also lead to topsoil loss.
According to the project, that area of Jordan gets 100mm per year of rain. The Salton sea gets under 75mm per year, so less than 3/4 of that. It appears that this part of Jordan is also significantly cooler and more humid, and has bodies of water within 100km. It also doesn't have a 3.5km high mountain range blocking clouds from passing over.
Unfortunately, the Salton sea has no water sources around it. There's no rivers, there's no Dead Sea. It seems like greening works best is places where there's enough water that tree roots can reach water. In Coachella Valley, the water is 300m deep, so no roots can reach it.
And, according to the desert greening project, greening increases rainfall by creating conditions more favorable for precipitation. The natural summertime relative humidity in the desert surrounding the Salton sea is as low as 4%, with 42C average temperatures. What are the practical limits when the water table is 300m below?
The valley only maintains current greenery by pumping huge amounts of water and constant watering, to the point where there's fogs in the morning caused by the pre-dawn watering. If greening could work in such extreme circumstances, wouldn't it be getting reversed already by this watering regime? Instead any small plot of land that isn't maintained is full of dead plants, even if they're drought tolerant species. Only a few kinds of desert plant native to the area seem to thrive.