I agree every shot is not going to be perfect but I'v worked with a whole lot of concrete and my exerience is that it's all about the penetration. Too much penetration and it blows out; too little and it falls out.
Whether it's a power fastner, a hard cut nail, a concrete nail, a redhead too close to an edge, etc. there will be success and failure.
The manufacturer of that product wants it to work for you and they put forth great effort and expense into telling you how their fastner works best. They want you to fall in love with it and keep buying it. If you follow their instructions you'll have the best results.
As to cure time, when you hear of "2,500 psi concrete" that's a projected 2,500 psi compressive strength at 28 days. Concrete continually hardens even after decades of being in place. When we do test cylinders in the field and break them in the lab, we do 7, 14, and 28 day test cylinders plus one spare. When we break those cylinders at 7, 14 & 28 days, it's almost guaranteed that you're past your 28 day design strength at 14 days and often you're there or really close on the 7 day break. If you're working on what we call a threshold building in Florida (highrise, any building with 300 people in one room, and some other buildings) those cyliders are tested prior to removal of the supports for the formwork. Once that's done you're certainly good to go. As to connection failure due to concrete not being sufficiently cured, I haven't heard of that and if it happens I'm sure it's quite rare.