actually you can have single editor reviews, here is the official guidelines from google
Usage guidelines
The goal of a review rich snippet is to provide users with review information about a specific product or service, such as the star rating (1 to 5 stars) and the name of reviewer(s).
The following guidelines apply to review snippets:
When using review markup, the main topic of the page needs to be about a specific product or service. For example, using review markup on a page containing multiple products is not supported.
Review of adult-related products or services are not supported.
If the markup contains a single review, the reviewer’s name needs to be a valid name (Person or Organization). For example, “50% off until Saturday” is not a valid name for a reviewer.
You can mark up either individual reviews (for example, an editor’s review of a product), or aggregate review information—for example, the average rating for a local business or the total number of user reviews submitted.
Use the individual Review format for pages containing a single review. For pages containing a collection of reviews, use the Review-aggregate format. If your page contains both (for example, an editor’s review plus a set of user reviews), we recommend picking one format. Use the individual Review format to mark up the editor’s review OR you can use the Review-aggregate format to summarize the set of user reviews. If a page contains both types of markup, Google will use the Review-aggregate markup for display.
