confusing exception handling with futures

confusion.dart

class ApiException implements Exception {
  ApiException();
}

Future<void> inner() async {
  throw ApiException();
}

Future<void> _middle() async {
  try {
    return inner();
  } on ApiException catch (e) {
    print('inner: $e');
  }
}

Future<void> outer() async {
  try {
    await _middle();
  } on ApiException catch (e) {
    print('outer: $e');
  }
}

void main() async {
  await outer();
}