I think you may have misunderstood. He is referring to the data, not the code. That data is usually user-specific and using a "script tag pointing to a popular CDN" is very unlikely to be workable.
He's referring to both actually. No external resources means that the page he's testing contains all of: html boilerplate, templates, data, script that puts it together. Comparing that to an equivalent page with everything rendered is kind of like comparison between a static "hello world" page to a cms rendering a "hello world" page.
In reality you're likely to have the templates already cached from previous requests and the templates rendering framework available from a CDN. What you end up transferring to the user is actually the data + tiny part of the script that gets rendering started.
Comments
I think you may have misunderstood. He is referring to the data, not the code. That data is usually user-specific and using a "script tag pointing to a popular CDN" is very unlikely to be workable.
He's referring to both actually. No external resources means that the page he's testing contains all of: html boilerplate, templates, data, script that puts it together. Comparing that to an equivalent page with everything rendered is kind of like comparison between a static "hello world" page to a cms rendering a "hello world" page.
In reality you're likely to have the templates already cached from previous requests and the templates rendering framework available from a CDN. What you end up transferring to the user is actually the data + tiny part of the script that gets rendering started.