It is primarily a job for EREL. I think that this assurance by Google, is comforting:
Keep in mind, with app bundles, you don't need to build, sign, upload, and manage APKs for each device configuration your app supports. You still build and upload only a single app bundle for your entire app, and Google Play takes care of the rest for you. So whether or not you plan to support devices running Android 4.4 or lower, Google Play provides a flexible serving mechanism for both you and your users.