Google is always experimenting with new features, not just in the Play Store, but across all of their products. Sometimes these experiments never become full throttled features, but they do tell Google quite a bit about them. In terms of whether it would be a good feature to add, or what they can do to make it even better, etc. It appears that Google is now working on a new feature for the Play Store, which is review highlights. Now reviews are a very important process of buying anything. Even if it's a $0.99 app in the Play Store. We all read the reviews to see if it's worth downloading and wasting our time with it or not. And review highlights are set to make that even better for users.
Review highlights are essentially quotes that are pulled out of the full review that users leave on app pages, and tell the user reading them basically all they need to know without dabbling too far into reviews. For example, "....In this version of the app, I have lots of video problems..." that tells you a few things. One, issues started with the latest version of this particular app. Two, there are issues with the app, which hopefully the developer is on top of. And that was all done without reading a long review of the app. Making everything easier for users.
Google appears to be experimenting with this feature for now. And that only a limited number of users are seeing these review highlights as of now. Which is why it's an experiment and not a full-fledged roll out of review highlights in the Play Store. More than likely, Google is dogfooding this update to those that work at Google, to get feedback and such, before they roll it out to everyone. It's too soon to tell if this will ever actually make it to the Play Store, but it likely will. Especially if the feedback that Google receives is good, in regards to Review Highlights. It's a great way for users to see what's good and bad about the app or game, without having to read a bunch of lengthy reviews on the app.