You are correct. I knew that google was showing brands like the redfin example, but when I saw the opensearch xml document, I assumed it was a way to relay more meta information to google.

It appears that the actual purpose of the opensearch xml document is to describe the search engine which exists on the homepage of airbnb.com. That explains why more sites don't do it. It isn't actually relevant unless you are running a custom search engine.

We have updated the blog post, and I'm sorry for the confusion about this point. Still, I very much believe in the takeaway message that it is important to craft a strong title for your website.