The idea of adding hydrogel to your soil isn't entirely new (you might be able to get some at your local garden supplier), what they are suggesting seems to be

The idea of adding hydrogel to your soil isn't entirely new (you might be able to get some at your local garden supplier), what they are suggesting seems to be about the mechanism - absorb moisture during the night, release during a dry day. Which sounds good, but I wonder how well that works once you have bigger plants and more than 10g of shallow soil per plant.