Android COVID-19 Exposure Notification API [pdf]

Can anybody tell me where the change will be? With [1] I've saved every apk with "play" in its name (Google Play Store, Google Play Music, Google Play services and Google Play Movies & TV). If the update happens, could I revert the changes by installing the extracted .apk files? Also, I've disabled the Play Store because my guess is that the Play Store will install the new API. After all, the Play Store also installs/updates regular apps. Can you tell my if my guess is correct?

[1] https://f-droid.org/en/packages/axp.tool.apkextractor/