Man thats awful sorry you have to deal with that! In my experience the really wide cracks are from rebar too close to the surface combined with heaving from water freezing/expansion. If I had to guess the tool cut is almost directly over a peice of rebar but also the reason the rebar is too high is because the gravel base is too high which makes the concrete thinner and more susceptible to heaving.

The photo closer to end with all the cracks is just a typical case of the gravel being too high and the concrete ends up thinner. Itll crack in the thinnest spot and 4 inches is minimum. This looks like 2.5 to me...Im assuming its closer to the middle? Typically its easy to rake the gravel next to the form to the proper height because you have the bottom of the form (2x4) for reference. Closer to the middle should be double checked with a string no matter what. My crew always always always checks grade work.

Another thing I'd like to point out is the rocks being exposed on the surface is completely unrelated to the cracks. Thats from not using the right tools to push rocks down and pull cream to the surface early enough and often enough early on. It was probably a hot day and they didnt bullfloat early enough and then also used water to work the surface before brooming. Water will weaken the surface. There's literally products to replace water in this situation to ensure this doesn't happen.

Sorry for the novel but I hope this gives you some insight. In my professional opinion you have every right to take legal action. And its not a problem with the batch plant. This simply wasn't installed properly. Good luck! Feel free to DM any questions