NS_SWIFT_UI_ACTOR in Objective-c protocol

I have an objective-c protocol:

@protocol MyDelegate <NSObject>

- (void)presentationFunc1:(MyViewModelType)viewModel;

- (void)presentationFunc2:(MyCompletionBlockType)completionHandler;

@end

These functions should be called on the main thread only. Since this protocol is implemented by objects in Swift files, I want to make it a @MainActor protocol.

I tried both the approach of adding:

NS_SWIFT_UI_ACTOR @protocol MyDelegate <NSObject>

- (void)presentationFunc1:(MyViewModelType)viewModel;

- (void)presentationFunc2:(MyCompletionBlockType)completionHandler;

@end

And:

@protocol MyDelegate <NSObject>

- (void)presentationFunc1:(MyViewModelType)viewModel NS_SWIFT_UI_ACTOR;

- (void)presentationFunc2:(MyCompletionBlockType)completionHandler NS_SWIFT_UI_ACTOR;

@end

And in both cases, while I do see some effect**, there's no nonisolated context error when calling those methods outside the main thread.

I also tried defining a similar protocol in Swift:

protocol MyDelegateSwift: NSObjectProtocol {
  func presentationFunc1(viewModel: MyViewModel)
  func presentationFunc2(completionHandler: MyCompletionBlockType)
}

Attempting to call presentationFunc1/2 outside the main thread does result in the desired Call to main actor-isolated instance method 'presentationFunc...' in a synchronous nonisolated context error.

**What I do see is that another object of mine, let's call it MyMainActor, that is a main actor and implements this method, no longer shows the following warning: Main actor-isolated instance method 'presentationFunc1(with:)' cannot be used to satisfy nonisolated protocol requirement; this is an error in the Swift 6 language mode. So it does have some effect, but still not showing the desired isolation error.

Can someone shed some light on this?
Thank you!