SwiftUI .backgroundTask requires registering and providing a handler

Hi I tried adding the new .backgroundTask modifier to my project but it still requires calling

func register(forTaskWithIdentifier identifier: String, using queue: DispatchQueue?, launchHandler: @escaping (BGTask) -> Void) -> Bool

without it I get the error No launch handler registered for task with identifier... but providing a launchHandler doesn't make any sense as it's handled in the .backgroundTask closure.

Am I missing something here? also can it be used for BGProcessingTasks as well, the WWDC session didn't mention that

Radar/Feedback Number: FB10249217