That's awful. The styrofoam forms they used weren't strong enough or weren't attached at sufficiently close intervals to prevent the bowing. They need to come back and grind it back smooth and straight.
It's not just the bowing... the brushing is bad, the control joints don't look good, there are chips and rough spots, and that's just what I can see in the pics. Totally unacceptable and in no way are any of those things normal. There's no fixing all that. I just wrote this in another's thread: it's not wood! You don't get close and then go back and cut and grind and sand and reshape, whatever. Concrete is supposed to look the way it's supposed to look just before it sets up. You don't go back and "adjust it" after that. Who was responsible for locating the spa cut out? Also unacceptable. Reject the work. Don't pay him. It's a redo.
In looking at the first photo, even if the deck were in line with the string laid out - the spillover looks too far away. I have no idea if it is, but to my untrained eye (I do not have a spa) it looks like the water will struggle to get into the pool without a lot of splashing on the deck.
I am only asking to give the OP some more ammo to go after the installer.