They're not telling you how to compose a video. They're giving you something to compare with as you compose your video. Too many other details will emerge, so i

They're not telling you how to compose a video. They're giving you something to compare with as you compose your video. Too many other details will emerge, so it's a guideline and not a how-to. And, later, those guidelines give a designer an institutionally-bought-in way to talk to someone without talking down to them. Refer to the guideline and discuss the guideline, not "I'm right, you're wrong." It's not meant as purely a technical spec as it may be interpreted by more tech-oriented mindsets IOW.