You didn't know about that Opensearch trick because it's not actually true... it doesn't really work. Google acquires page titles from a variety of sources, including Dmoz, domain name, and inbound links.

For example: Search for [msnbc], and it shows up as “msnbc.com” … title tag: “Breaking News, Weather, Business, Health, Entertainment, Sports, Politics, Travel, Science, Technology, Local, US & World News – msnbc.com”

[new yorker] shows up as “The New Yorker” … title tag: “National and world news, Profiles, culture, reviews, fiction, poetry : The New Yorker”

[redfin] shows up as “Redfin” … title tag: “Search Homes for Sale & Find Real Estate Agents Who Put You First | Redfin”

None of those pages have opensearch documents.