I basically agree with the statement that the fingers "being" doesn't convey much in itself. I haven't read the article, and don't see this issue as having anything to do with YA, but why waste a verb to describe? You end up with a sentence that does nothing but say the fingers "were" that?
"His shriveled and blue fingers still gripped the amulet, even in death" or "The old man's fingers, shriveled and blue, were cold against her cheek" or whatever. That does two things, one of which, I think is what the author was talking about, the other is moving description to action, which I think makes both the description and action better.