This seems to have been an oversight on my part. See from section https://github.com/flutter/flutter/blob/c04cd2b18ebfe30b0b6d82d0b73667eb437cd7f7/dev/devicelab/bin/tasks/build_android_host_app_with_module_aar.dart#L224 and on. In particular, reference the build.gradle for the host app https://github.com/gmackall/flutter/blob/master/dev/integration_tests/pure_android_host_apps/android_host_app_v2_embedding/app/build.gradle which is clearly following the instructions from the "module source code" section in https://docs.flutter.dev/add-to-app/android/project-setup#add-the-flutter-module-as-a-dependency and not the depending as an aar.