For many assets yes, and it's something I do quite regularly.

But many assets (especially CSS) rely on relative files - and we have apparently collectively decided that directories or other bunches or files is somehow a totally different thing than a file and need fundamentaly different logic - so just using the CDN makes you not have to worry about this.

Yes, of course. I think he means all the to manage a big project's dependencies. For a small or static website, you could manage all of those manually.