He may just talk like that, but I think Doctorow is going through, as comprehensively as his allotted time slot will allow, the talking points he and the host have prepared beforehand. Keeping this in mind and taking into account the audience likely doesn’t know what a “protocol” is, I think it’s fine that he doesn’t mention ActivityPub. Perhaps he mentions it in his book. I’ll check it out if it lands in my local library’s bookshelves.