7D Mark II Video - Save to Multiple Cards

I have a 7D Mark II. I can set the camera to save pictures to both cards at once, but not video... is this normal or am I missing something?

The camera saves videos to the card selected for playback, even when it's set to record images to both.

The cards are both Lexar, a 633x SD and 800x CF. It will save to either card, but not both simultaneously.

Thanks