Yes, you read that title correctly. Editors should not focus on the grammar.
A copyeditor for The Daily Californian takes a hard look at copyediting and grammar’s role in the editing process. From the title of his article, I think you can see what his views on the matter are.
Near the end of the article, he got to the crux of the matter:
“…what constitutes the soul of writing is the message, not the often-tedious rules we attribute to helping us understand it.”
Focus on the content. A couple of years ago, I wrote a post stating that technical editors do not need to be grammarians, which was my polite way of saying that we don’t have to be pedants about what so many people hold near and dear to their hearts.