below is a code snippet from a tutorial I am trying to learn.
appreciate if you could tell me why we are not using protection : asyncvalue.guard inside build() but later used when calling the same method?

@riverpod
class WeatherFirst extends _$WeatherFirst {
  @override
  FutureOr<String> build() {
    return _getTemp(Cities.seoul);
  }

  Future<String> _getTemp(Cities city) async {
    await Future.delayed(const Duration(seconds: 1));

    switch (city) {
      case Cities.seoul:
        return '${city.name} - 23';
      case Cities.london:
        throw 'Fail to fetch the temperature of ${city.name}';
      case Cities.bangkok:
        throw 'Fail to fetch the temperature of ${city.name}';
      case Cities.tokyo:
        return '${city.name} - 28';
    }
  }

  Future<void> getTemperature(Cities city) async {
    state = const AsyncLoading();

    state = await AsyncValue.guard(() => _getTemp(city));
  }
}

i tried inserting various error scenarios code works fine