I have the UK version and have been using Nova Launcher for a few weeks now. I have never had the issue you are experiencing, even when using Bluetooth toggles mentioned above. So I don't think it's a bug in EMUI.
Have you made sure that Nova is not in the list of apps that are aggressively stopped in Phone Manager's battery/power settings? Also try signing up for Nova Beta in the Play Store which I have done. You might get a build that fixes something causing your issue.
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