I was able to find no scientific research to support their use in home gardens.  Most of the research is based on ancient methods of using electricity to stimulate plant growth.  Some say it helps plant seeds germinate. Others suggest that it can increase yields. Some research is on their use in hydrophonic gardening.  However these are not well controlled studies or even published in peer reviewed scientific journals. And they are usually restricted to one crop results.  I could not find one research study on their use in home gardens and/or with multiple plants.
See:  https://gardenprofessors.com/electroculture-rediscovered-science-or-same-old-crap/