Yes, and he's making the point that it manages to work. And that perhaps your expectation should be the same for a chat client as for an email client. Which may or may not be a valid point.
And without proper mailing-list-moderation, that too can cause email storms. No one blames "the genius who decided to put everyone in one mailing list" when that happens.
The real fail here isn't putting everyone in one channel. The real fail is not using/providing proper admin tools
I'm going to guess you could also break IBM's phone system by attempting to start a conference call with 200K people on it, and destroy their auditorium by putting too many people on the stage.
Although usually only a limited number of people can post to an "announce-list" that goes to everyone in the company. (And if there are company-wide lists that anyone can post to, most users filter those to a folder. I suspect such lists don't scale past a certain point either.)