I'm not sure of a more eloquent way to say this. Comcast's customers are the CDN's customer's customers.

To play devil's advocate, those CDN customers would also be unable to access content if their power went out. But nobody would think to say the CDN isn't doing their job if Texas had a blackout, because "I'm paying you to deliver my content to Texas, dammit!"

It's a bit of a stretch, but I think that's the analogy they're going for.

Right, but that relationship, especially as applies to support and subscription, is not transitive.

How do you depeer my customers' provider without depeering my customers? How do you cut off a router's network access without cutting off access to the networks behind it? How do you blacklist a /8 but not one of its /24s without an exemption list? How do I prevent Bob from forking my code, but allow people who fork from Bob to fork the modifications he would do to my code? How do you join tables on 2 databases when you can't authenticate to the first?