Aren't they supposed to be nearly invisible? I had one done before, and I could hardly see it. He waited while the filler set, cut it with some razor sharp thing, and polished it.
Had one out today, and you can still see a dint in the surface, and a single crack, like a white flake within the glass when viewed from a certain angle. Better than the white ball of cracks that were there originally, but if it was in the swept area of the screen, it would probably fail the MOT.
The windscreen company said that's how they do it, and they don't polish it because it would be distracting while you were driving (like a crack isn't!).
It sounds to me like they do a crap job of chip repair so they get a replacement job when the repair is not good enough.
Bob