AVAudioPlayerNode scheduleBuffer & Swift 6 Concurrency

We do custom audio buffering in our app. A very minimal version of the relevant code would look something like:

import AVFoundation

class LoopingBuffer {
  private var playerNode: AVAudioPlayerNode
  private var audioFile: AVAudioFile

  init(playerNode: AVAudioPlayerNode, audioFile: AVAudioFile) {
    self.playerNode = playerNode
    self.audioFile = audioFile
  }

  func scheduleBuffer(_ frames: AVAudioFrameCount) async {
    let audioBuffer = AVAudioPCMBuffer(
      pcmFormat: audioFile.processingFormat,
      frameCapacity: frames
    )!
    
    try! audioFile.read(into: audioBuffer, frameCount: frames)
    
    await playerNode.scheduleBuffer(audioBuffer, completionCallbackType: .dataConsumed)
  }
}

We are in the migration process to swift 6 concurrency and have moved a lot of our audio code into a global actor. So now we have something along the lines of

import AVFoundation

@globalActor public actor AudioActor: GlobalActor {
  public static let shared = AudioActor()
}

@AudioActor
class LoopingBuffer {
  private var playerNode: AVAudioPlayerNode
  private var audioFile: AVAudioFile

  init(playerNode: AVAudioPlayerNode, audioFile: AVAudioFile) {
    self.playerNode = playerNode
    self.audioFile = audioFile
  }

  func scheduleBuffer(_ frames: AVAudioFrameCount) async {
    let audioBuffer = AVAudioPCMBuffer(
      pcmFormat: audioFile.processingFormat,
      frameCapacity: frames
    )!
    
    try! audioFile.read(into: audioBuffer, frameCount: frames)
    
    await playerNode.scheduleBuffer(audioBuffer, completionCallbackType: .dataConsumed)
  }
}

Unfortunately this now causes an error:

error: sending 'audioBuffer' risks causing data races
   |                      `- note: sending global actor 'AudioActor'-isolated 'audioBuffer' to nonisolated instance method 'scheduleBuffer(_:completionCallbackType:)' risks causing data races between nonisolated and global actor 'AudioActor'-isolated uses

I understand the error, what I don't understand is how I can safely use this API?

• AVAudioPlayerNode is not marked as @MainActor so it seems like it should be safe to schedule a buffer from a custom actor as long as we don't send it anywhere else. Is that right?
• AVAudioPCMBuffer is not Sendable so I don't think it's possible to make this callsite ever work from an isolated context. Even forgetting about the custom actor, if you instead annotate the class with @MainActor the same error is still present.
• I think the AVAudioPlayerNode.scheduleBuffer() function should have a sending annotation to make clear that the buffer can't be used after it's sent. I think that would make the compiler happy but I'm not certain.
• Am I overlooking something, holding it wrong, or is this API just pretty much unusable in Swift 6?
• My current workaround is just to import AVFoundation with @preconcurrency but it feels dirty and I am worried there may be a real issue here that I am missing in doing so.