比較的新しい、ビデオ説明に関しての制限です。
アプリ以外の映像を入れてはいけない。
（訳注 たとえば、風景のイメージショットとかでしょうね）
ただし、ナレーションや文字を入れても良い。
原文
2.3.4 Previews are a great way for customers to see what your app looks like and what it does.
To ensure people understand what they’ll be getting with your app, previews may only use video screen captures of the app itself. Stickers and iMessage extensions may show the user experience in the Messages app.
You can add narration and video or textual overlays to help explain anything that isn’t clear from the video alone.