I would never leave a customer with that for a finished job, however as far as your rights go, I think they are allowed to walk away from it as its non structural. If they happen straight after the pour I just cut some panels out and do it again. They probably poured sloppy concrete on a windy day and the surface dried out too quickly, hence the spider web type pattern to the cracking.. Sealer doesnt fix cracks.
The sawcuts look pretty far apart lengthways, should be under 3m spacings,.