I agree with most of the article but displaying a static 5-star image on your website when your real rating is 4.6 stars (should be displayed as 4.5 star image) is rightly called out as disingenuous.
If you really want it to be efficient display a static "cached" image of the rating and swap it for the iframe once the image is loaded and displayed. This ensures fast response time and accuracy of the fresh rating at the same time.