Swift Concurrency: Feedback Wanted!

Experimenting more with @MainActor and view controllers, the following compiles and prints main thread: false.

class ViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    DispatchQueue.global().async { self.mainActorIsolated() }
  }

  @MainActor
  func mainActorIsolated() { print("main thread: \(Thread.isMainThread)") }
}

It does not compile for a similar class that does not inherit from UIViewController (Call to main actor-isolated instance method 'mainActorIsolated()' in a synchronous nonisolated context). Is this a bug?