I read the shtick under the order form. They claim the bugs are raised more slowly on a diet closer to wild insects which actually causes there "Body tissues" to be more nutritional. They claim it does not wear off like dusting and gut loading.
I grab the free ones at every show! They are fed a special chow. I don't put much stock in it and gut load and dust my feeders as I normally would but they do seem to have less die-off. I got crickets from Josh's Frogs awhile ago bc I was buying other stuff from them and they are still going strong! I wouldn't rely on their claims but I am happy with vitabug as a company.
I am not aware of anything that leads me to believe the claims as of right now. So far as I know, from the peer reviewed literature I am aware of, that 24-48 hours prior to feeding is the critical gutload time for commonly used feeder insects.