https://wccftech.com/google-messages-on-galaxy-s21-is-getting-a-one-ui-inspired-design/

In February this year, I talked about hidden system setting design elements in Android 12 that Samsung's One UI inspires. While at that time, we thought that this would be an oversight or just an experiment from Google, it seems like the feature is now available in Google Messages. Still, at the time, it is only available if you are using a Galaxy S21 device.

This change first appeared when users on Reddit started talking about how Google Messages is now showing a similar theme to the overall design elements of the One UI.