you are correct that you CAN - but who does. That's no longer considered best practice. The arugment these days is that it's a lot easier to manage css if it's in a separate file, same with js, etc. So none of the serious web developers actually do anything inline anymore. The time it would take to convert a "best practice" website with separate files for html, css, js, etc. is just not worth it. The point he's making is still valid - why not have the option for something static.
But with the same (and even much bigger) success you can declare “I’m switching to self-contained HTML! No more external resources!” instead of “I’m switching to PDF, saying farewell to interactivity and mobile devices”.
It's just the declaration of ONE person, switching ONE site.
