I don't know that you are being overly picky. I definitely see and it definitely looks worse with the white light.
As it is a hand applied finish, there very well may be some blemishes in it. In this unfortunate case, it happens to be in a very noticeable spot, due to the way the lighting hits it. I believe if it were further away from the steps (towards the right in the photos), you may not have noticed it. It definitely wouldn't have been as noticeable. Honestly, if you hadn't circled it and said it was an issue, I wouldn't have picked it out as a problem.
I agree with the installer. I think patching it would make it look worse. In this case it is now part of the character of your pool. You will most likely be the only one who notices this, as it is your pool and rightfully so, you are being critical of the product. This is one of those things to which I say "if anyone brings it up, I'll throw them out!" because I know it is something that only I am going to be picky about. Everyone who is enjoying your pool and hospitality aren't even going to notice.
If it is any consolation, my pool has an ever so slight boot mark that I can only see at night when the lights are on. I don't particularly care for it, but trying to fix it would have made it much worse. And in the 2 years it's been there, nobody has mentioned it to me.
--Jeff