How to save 4K60 ProRes Log Video Internally on iPhone internally?

Hello Apple Engineers,

Specific Issue:

I am working on a video recording feature in my SwiftUI app, and I am trying to record 4K60 video in ProRes Log format using the iPhone's internal storage. Here's what I have tried so far:

1. I am using AVCaptureSession with AVCaptureMovieFileOutput and configuring the session to support 4K resolution and ProRes codec.
2. The sessionPreset is set to .inputPriority, and the video device is configured with settings such as disabling HDR to prepare for Log.
3. However, when attempting to record 4K60 ProRes video, I get the error: "Capturing 4k60 with ProRes codec on this device is supported only on external storage device."

This error seems to imply that 4K60 ProRes recording is restricted to external storage devices. But I am trying to achieve this internally on devices such as the iPhone 15 Pro Max, which has native support for ProRes encoding.

Here are my questions:

1. Is it technically possible to record 4K60 ProRes Log video internally on supported iPhones (for example: iPhone 15 Pro Max)?
2. There are some 3rd apps (i.e. Blackmagic 👍🏻) that can save 4K60 ProRes Log video on iPhone internally. If internal saving is supported, what additional configuration is needed for the AVCaptureSession or other technique to bypass this limitation?

If anyone has successfully saved 4K60 ProRes Log video on iPhone internal storage, your guidance would be highly appreciated.

Thank you for your help!