He’s not talking about self host as in CDN vs self host. It’s about not linking to third party assets. You link to yoursite.com/static/bootstrap.js, not someone

He’s not talking about self host as in CDN vs self host. It’s about not linking to third party assets. You link to yoursite.com/static/bootstrap.js, not someoneelse.com/shared/bootstrap.js. You can (should, as he says at the end) have this be through a CDN. Just use the same CDN you use for other stuff.