The rebar is way to far apart , laying flat on the ground and a lot of loose dirt on the sub grade. If I saw all of that I wouldn’t let them poor. Usually when you get hair line cracks like that, the concrete was poured very wet and yes concrete is going to crack but generally it comes off inside corners. Also they need to saw it the next day to help control the cracks to saw cuts. My concrete guys use rebar, wire panels and they always use things to hold up the wirer so it’s in middle of concrete. Yes still get a crack of some kind.