As bibirez suggests it's quite easy to produce an AAB by using the Android Studio export, but Ashley is correct that other than silencing that warning in the Play Store console there is little reason to do so at the moment. We can add additional notes to the tutorials and manual in this regard, and we probably should. However, I'm sure people will still be confused. Not everyone reads the manuals and it's easy to miss a small comment about the format. It also doesn't help that the warning on the Play Store console can appear to be preventing release to the untrained eye.
— We are aware of the update. It's technically cordova-android 8.1, we're already using the latest cordova-cli 9.0 (which uses cordova-android 8.0 by default). We are planning to update to use the latest version of cordova-android. However, we have a blocking issue to resolve prior to updating. We will have to do additional work to add support for the new format as well, so it will likely be available after we've updated to the latest cordova-android version.