I have a private app, so I can manage clients ad accounts to create custom audiences. I don't need more permissions than that.

My app has the Marketing API integrated, and the app has some requests for permissions in draft. I can't complete the review request because it's asking how the facebook reviewer can test the app. But the problem is that the app is private for clients only, so how can we do it?

Do I really need an app to get permissions to create a custom audience to my client's ad account using the Graph API?