If you are close enough to get to Graff in NYC, I guarantee there are many independent appraisers you could hire. You can look at the PS resources for appraisers linked at the top. Explain your worries when you call and you will be able to find someone who can do the entire appraisal without taking the stone out of your sight and someone who has a big screen connected to their microscope so they can show you the inclusions compares to the GIA report inclusion map so they can show you that it matches. Ask them to walk you through how to match the inclusions to the report, and then after they show it to you, see if you can do it yourself with only a loupe. Tell them on the phone when you call you want their help with all this - you may have to pay a bit more but once you learn how, you will have more peace of mind for every jewelry purchase or repair for the rest of your life.
Re: things appearing worse once set: when I got my mahenge spinel ring back from being set, I knew it was the same stone but I thought it had been damaged while the stone was away because it had a visible crack in it. HOWEVER since I was already a PSer at this point, I had taken lots of macro photos of the stone right after I bought it, including some face-down. When I went back and looked at them, yep, that was already there and didn’t look any worse at all. I had just never noticed during the multiple years I had the loose stone (during which time I looked at it regularly! For years! In the same lighting I then saw the ring in!).
It’s the line on the right side here, with another pic in the same light to show that it really easily hides:
Now for some pictures from the day I bought it, three years before getting it set:
You can clearly see the feather in the last two - but not at all in the first or second picture (the first is at the place where I bought it, and it was in my hands from when I first looked at it until after I got home). I just straight-up did not notice it for years until after I got it set. If I hadn’t had these pictures and a few I had taken through a loupe, I would have been sure either the designer or jeweler had damaged the stone. But my pictures show that has been there since the day I bought it.
Re: appraisal, it is also very common for sellers to overinflate the value they give you and tell you the stone is worth more than you’re paying for it. Which doesn’t really make sense from a business standpoint because I guarantee if they could actually get a higher amount for the stone they would - but it makes people feel better when buying. Again, this is very VERY common. How did the insurance appraisal compare to what he actually paid for the diamond? Was it in line with it or less than it? Because if it was in line with what he actually paid, or maybe 10-20% less, then that is also completely normal if your insurance appraisal was for replacement value. It wouldn’t indicate anything more than you paying a fair price or slightly over paying for the diamond (again, super common), not that it’s a different one entirely.