as the article correctly states, not all hydrogels are made the same. the ones in diapers and menstrual pads are specifically designed to NOT rerelease absorbed liquids. there are other hydrogels out there which are designed to absorb and dry out repeatedly without degrading or losing absorbancy, and are therefore more suitable for plants. i dont have any deeper experience with hydrogels, but I did have it as a consideration for my kratky (passive) hydroponics setup.