I'd tell him you know it's not normal to see the swirls. Tell him unless he 'fixes' it, you're witholding final payment.
You'd want to do this via certified letter AFTER you speak to another Floor Professional. Also, you want to document your case in a notebook. Write down dates and places and in what for your conversation(s) took place and whether or not they were in person, via phone, or at his office or what. SHOULD he sue you while you're waiting for him to come back, you'll have some PROOF for the judge to show you were dissatisfied. Just be sure to send the SAME envelope to yourself (and your COntractor), send it certified return receipt (but DON'T open up your copy.) The judge will then have more than he-said, he-said when it comes time to make his decision. Take still-pictures and even a video. You can even talk when you do the video. If you have to bring a TV and a VCR to court, tell the judge's Clerk in advance and do just that!
If the COntractor is saying that the swirls are 'normal' after the 'final coat' is applied, I'm sorry to say he's mistaken. I've seen buffed/waxed vinyl tile floors w/swirls in them. And I've seen them in my ice cream too. IF he makes a fix, tell him in your letter you'll pay him 15 days AFTER the fix. Also tell him in the letter that if you don't hear from him in 30 days, you will either consider the matter 'closed', and you'll have the right to 1) do nothing or 2) get it fixed. There's no need to tell him you'll sue him. If you word your letter about your feelings, about the results of your hardwood flooring research, and what you'll do and when, I think he'll get the message you MIGHT sue him if he 'does the wrong thing'.
My best to ya and hope this helps.
Jay J -Moderator
PS: Read the answer to Question 3. This should help: NOFMA.org. If they're not 'believable', who is???