There is a difference between what you see at Schema.org and what Google publishes at its Google Search developer documents for structured data rich results. The short difference is that what Google publishes is what you can potentially see surface in the Google search results but what schema.org publishes you probably won’t.
In short, if the structured data is not one of the dozens of structured data items listed in this gallery then you won’t have a chance of showing up with richer search results in Google Search. That means if you use something that is published on Schema.org but that is not listed at the Google developer site then you won’t benefit from the enhanced listing in Google Search. For example, you won’t see stars, reviews, carousel images, and other forms of richened up search results.
John Mueller, a Search Advocate at Google, talked about this in a video hangout on Friday, January 15, 2021. He was answering the following question at the 49:44 mark into the video. The question was “In the schema.org website, there are different suggestions for travel sector, such as tourist trip, travel agency, or trip. Are the schema types mentioned above supported or relevant for Google indexing and ranking? If not, what would be the most suitable structured data type for a trip landing page?”
Does Google support schema.org?
Google supports some of schema.org, but only those elements mentioned in the Google developer guides. John Mueller of Google responded in detail but summed it up saying “we support a subset of the functionality, or the different types of markup, from schema.org.” “And those are the things that we would show in the search results,” he added “and everything else is essentially kind of, I don’t know, more like a nice-to-have.”
Here is his full response:
So it’s important to differentiate between kind of the broader schema.org ecosystem, where there are lots of different ways that you can add structured data to individual pages, and the Google side of that, in terms of Google Search.
So in particular, we support a subset of the functionality, or the different types of markup, from schema.org. And those are the things that we would show in the search results. And everything else is essentially kind of, I don’t know, more like a nice-to-have, or more like something where you’re adding a little bit of extra information to your pages. But I would not expect to see any change in search because of that. And I think that refers to all three of those types in that sense.
So what I would recommend doing is going to our Search Developer documentation, and looking at the rich results types that we have listed there, and trying to work out which of these types map to the kind of content that you have, and then kind of focusing on those types first so that you kind of have the visible effect kind of nailed down and you kind of know that, if you spend time on that specific kind of markup, you will have a visible effect in search.
And then, if you want to go further and provide additional information through other schema.org types, you’re welcome to do that. I would just assume, by default, that you would not see any effect in search at all. So there is a slight sense of, well, we understand the pages a little bit better with more types of structured data on our page. But I would not assume that that’s something that would have a visible effect in terms of ranking or better visibility in search. So that’s kind of the direction I would go there.
Here is the video embed so you can watch it yourself:
Forum discussion at YouTube Community.