I think you've got a point with the "very high grade". This guy is an experienced seller of coins and should be able to offer a realistic actual grade such as VF/NEF, in his opinion, whilst allowing those interested to make up their own minds. Also, the fact he doesn't accept returns, is telling.
The photography isn't ace, but it's not that bad either - certainly enough to see that the obverse especially is not "very high grade".
With that said, I definitely wouldn't give him a negative. I'd take the hit knowing it was poor decision making on my part - "caveat emptor". Been disappointed several times myself, but ultimately know that really, I should have realised before I jumped in and bought.
I'd give him a less than ringing endorsement positive, such as "prompt delivery, coin well packed". Something of that nature. He'll get the message.