I agree with all he said.

I've never lived in the city of San Fransisco, but for may years close to it, beginning in 1961. I can't remember when I first saw it, or when I first ate it. My best guess is at least 50 years ago, not only in San Francisco (Fisherman's Wharf) but also in the surrounding area. I've also see Beef Stew in a sourdough bowl at Superbowl parties.

The one in the video is much larger than I've seen. Probably meant for people to share. I couldn't eat that much if it meant eating all that bread. I don't think of Clam Chowder as something that's better in SF than elsewhere, but that bread is special. It's been imitated but not duplicated elsewhere IMHO.