Appositive usage

I was reading a review of my friends indie fiction, and the reviewer claimed he was misusing appositives. I read the quote myself and I disagree with him, but I'm not sure.

[quote from review]
– An example of inappropriate appositive usage: “Sprawled out upon a hill, making it nigh impossible to see the grass underneath, were hundreds of thousands dead Soldiers.” An appositive generally implies the word “noun,” so we can just refer to an appositive noun as an appositive. This sentence does not do so, creating awkward wordiness that can be easily fixed. “The bookshelf, a modern piece of furniture, was moved into the house first.” is an example of proper comma usage for the appositive. There fewer of these, but they some times still appear in the story, breaking the flow.
[end of quote]

Is he right? Is this grammatically incorrect?