Thanks for your question. Unfortunately it is indeed a known issue that Covenant Eyes does prevent screen sharing or casting on Android. While our app is installed it will maintain it's hold on screen casting as that is how we are able to ensure Screen Accountability on the device.
And you are correct. A device cannot cast multiple sources simultaneously. While Covenant Eyes is installed on an Android™ that device cannot use its normally screen casting feature and for that I do apologize.
Thank you again for your question and have a great rest of your day.