No excuse for the chipping, just not using good tools or good practice.
A decent wet cutter will leave nearly a factory edge on soft ceramic.
A quality continuous rim blade on a grinder will do just as good with a steady hand.
A quality score and snap cutter with a wheel suitable for ceramic should be cutting with minimal chipping.
Even if the cutting tools let you down. A diamond pad, sanding block, or even the right grit of sandpaper will tidy the edge. All it takes is patience.
We see a lot worse in here, but your paying the bill, so if your not happy take IT up with him.
The customer has to take a part of the blame, but in my Veiw, you shouldn't advertise yourself to be able to do something you can't.