A customer recently emailed me about their frustration with how Google ads use review data:
Amazon competes with me for the term in paid ads. They say [CUSTOMER's TRADEMARK] and show their star rating in the ad. But the stars have nothing to do with a product, but for Amazon itself. I think it's very deceptive to consumers! We don't sell on Amazon, so the ad leads them to competing products.
The keyword you said is "paid ads".
When it comes to paid ads, all the rules are different.
Google has pushed stores to buy ads for years by making their Rich Results a bit weaker than other data types.
e.g. Recipes, Movies, Articles, Books, etc all can get into that top #0 spot in Google with structured data and Rich Results alone. But not products, they are only available in the regular search results because Google's Ads occupy the top #0 spot for product based searches.
It sucks but ad revenue is Google's golden goose.
Google has rules around getting those reviews into their ad system but they are different than the organic/structured data. It's also possible for stores to use their store reviews on ads for a product, which is how the results look deceptive from Amazon.
In the organic search results, most sites are held to the same standard. I've seen some "interesting" results from Amazon and Etsy that makes me think they have special agreements with Google, but those are the only two sites I've seen like that. Even the big ones tend to follow the same structured data rules.
JSON-LD for SEO is the safe, effective, and fast way to win Rich Results from Google. It's helped thousands of stores acquire Rich Results since 2015, often faster than industry averages.