Why does @available not work?

Hi,

I'm trying to build a react native project on Xcode 10.1 with IOS 12.1. I am using Mac OS 10.13.6 (hence the old Xcode). Whenever I build it, these errors appear regarding the @available(iOS 13.0, *) condition.

The path to the below error: Pods > Development Pods > react-native-maps > AIRMAP.m > -setUserInterfaceStyle:

- (void)setUserInterfaceStyle:(NSString*)userInterfaceStyle
{
  if (@available(iOS 13.0, *)) {
    if([userInterfaceStyle isEqualToString:@"light"]) {
      self.overrideUserInterfaceStyle = UIUserInterfaceStyleLight;
    } else if([userInterfaceStyle isEqualToString:@"dark"]) {
      self.overrideUserInterfaceStyle = UIUserInterfaceStyleDark;
    } else {
      self.overrideUserInterfaceStyle = UIUserInterfaceStyleUnspecified;
    }
  } else {
    NSLog(@"UserInterfaceStyle not supported below iOS 13");
  }
}

I understand why it is failing, properties such as overrideUserInteraceStyle don't exist pre IOS 13 dark mode. However, I don't understand why the @available tag is not preventing Xcode from entering that code block. I have tried New Build & Legacy Build. I have set the project format to Xcode 10.0-compatible. Xcode 9.4+ should support @available.

How can I resolve this error on Xcode (other than by commenting it out)?