Before you say that this feature was already rolled out to users, you should also know that there was a condition to be fulfilled before you can opt-into auto archiving. The condition was - have very low storage so that Google can show you an opt-in dialog while installing an app.

But now Google has started rolling it out to everyone now and having low storage is not a requirement anymore. You can directly opt-into Auto-Archiving from the Google Play settings, Settings > Automatically Archive Apps. I have it on 37.4.* version of Play Store and also in 37.5.24 (available on apkmirror).

While this feature works when you have low storage, you can check archived apps by going into the Manage Apps & Games section then tapping on the Manage tab. Any archived will have an icon as well in your app drawer and tapping on it will start the reinstall process.