There's an old paper on that networking, by design, is not reliable or efficient - which is more cogent than ever in large scale distributed systems. What Comcast would cite would likely be that, so I doubt it would reveal the quiet part said out loud about the reliability of Comcast's services.
Jokes aside, that paper is very worth reading. And HN readers will recognize one of the authors as the creator of Jepsen, of distributed database testing fame.
A couple citations I liked:
https://queue.acm.org/detail.cfm?id=2655736
https://blog.acolyer.org/2014/12/18/the-network-is-reliable/