Task (on MainActor) may be executed other than the main thread.

[soranoba]

Describe the bug
Task (on MainActor) may be executed other than the main thread.

Task {
    do {
        // It should do anything on main thread.
    } catch {
        // It should do anything on main thread, but sometimes executed on other than the main thread.
    }
}

To Reproduce
All code is here on the branch in the repo.
https://github.com/soranoba/iOS-SandBox/tree/TaskMayBeExecutedOtherThanTheMainThread

    @IBAction private func didTapStoreKitCase(_ sender: UIButton) {
        Task {
            do {
                print("SK-1: isMainThread = \(Thread.isMainThread)")
                let vc = SKStoreProductViewController()
                _ = try await vc.loadProduct(withParameters: [SKStoreProductParameterProductIdentifier: "xxxxxx"])
            } catch {
                print("SK-2: isMainThread = \(Thread.isMainThread)")
            }
        }
    }

It should output:

SK-1: isMainThread = true
SK-2: isMainThread = false

Expected behavior

It should output:

SK-1: isMainThread = true
SK-2: isMainThread = true

Environment (please complete the following information):

• OS: iOS 15.4
• Xcode Xcode 13.3.1

[soranoba]

Reproduced 100% with SKStoreProductViewController.loadProduct (withParameters :), but never reproduced with other methods 🤔