I get the idea that these are intended to be temporary beds that you can put together quickly and without much preparation. The fact that they are doing this over grass in the pictures makes me think of a sandwich garden where you lay down corrugated cardboard over the area you want to turn into garden bed, then layer garden soil, peat moss, and compost over it up to six inches deep, then plant in it (you may have to dig through the cardboard to plant some larger plants requiring greater planting depths). The cardboard kills off any lawn/weeds beneath it, then composts away, leaving a nice, permanent bed.
We’ve done modifications of the sandwich idea in several places in our yard, and it works fairly well. Their instant garden idea seems quick and easy, but I can’t help but think it would get messy after awhile and you’d end up wishing you’d put a firmer barrier around it. But then their focus seems to be more emergency situations, in which case who cares if it’s tidy? In any case, it’s an interesting idea, and I hope they keep their promise to follow up through the year.