John Mueller of Google said in that video hangout at the 39:51 mark that Google is trying to "recognize additional details about author information, information about reviewers, about the website in general, through a number of ways".
We try to recognize such additional information about information about the author, information about the reviewers, about the website in general, in different ways. Partially through the content directly. So similar to how users would see it when they go to the page and they see kind of information about who has reviewed this content or who has provided it. That is really handy.
If the net is hidden in structured data, that is not very convenient for users, because users tend not to use the display source when viewing a page to determine if they should trust it. So I would try to find an approach that works especially well for users and focus on that.
This is similar to what we wrote when we talked about Google: YMYL sites must have an expert to write the content and detect and rank Google algorithms for YMYL searches.
The question is how Google does this? John said "in different ways". "Partially through the content," he added, but also said that only structured data is probably not the best way to transfer this information to Google in a trusted way.
Hat tip for Glenn Gabe:
Worried about E-A-T for a medical site? JM: Google attempts to identify additional details about the author, medical reviewers, about the site (and partially directly through the content) in a number of ways. So, similar to how users would see it: https://t.co/oK0jssHP0d pic.twitter.com/ubfhgQ0zF7
– Glenn Gabe (@glenngabe) August 12, 2019
Forum discussion on twitter.