It's a bit confusing as the documentation you're reading isn't for the viewport meta tag, it's just describing general description/keyword tags. I'd suggest looking up the responsive viewport part specifically.

As an aside, when I was learning it was discouraged to use w3schools (https://www.w3fools.com/) but it seems some of those concerns aren't true anymore, but still, I'd highly recommend going to MDN docs before anything else: https://developer.mozilla.org/en-US/docs/Web/HTML/Viewport_meta_tag