This should still be an option for people who are using only one H9. Not being able to switch back and forth is a major showstopper.
Well, unfortunately, this is not something that you can control from software. There's a settings file that gets submitted with the app that says whether the app supports background mode or not, and you can't override that setting from software. So, there's no mechanism for us to allow some users to opt into this and others not to.