In my experience, not a problem at all. I've reared two species from eggs to adults and reproduction as well using Miracle Gro and two-three different brands with nutrition capsule as well as perlites (white stone-like in size of about 1/8 - 1/16 inch) with NO PROBLEM. I reared Dynastes tityus and Strategus aloeus until emergence without any problem. You can use it for female to lay eggs as well. I reared hundreds of of D. grantii larvae with it. I never emerged any D. grantii only because I gave all my larvae away to colleagues and other beetle enthusiasts in past, and I'm currently rearing couple tens of larvae with those garden soil (the potting soil, not topsoil or anything non-plant materials). Of course, I do rear some others with my own fermented substrate as well too.
However, I did experienced specimens from potting soil did not emerge in average time period compared to the ones reared in fermented oak substrate. They also took from couple months to even an year to develop enough to emerge as adult beetles. It seems potting soil just don't have enough nutrients for scarab rearing, but still edible. If you did not prepare substrate, then I guess this can be your alternative.