According to this article:
With iPhone Mirroring, you can wirelessly interact with your iPhone and its apps and notifications from your Mac. Your iPhone stays locked, so no one else can access it or use it to see what you’re doing.
support.apple.com
there are settings in the iPhone Mirroring app that offer options like "Ask Every Time" and "Authenticate Automatically". What do your settings currently show?
I found that page with search terms:
iphone mirroring