Request Camera Permission on iOS in Unity at Runtime

Our application built in Unity uses ARKit/FaceTracking on iOS.
We would like to request the Camera Permission at runtime immediately before it is used – and not on application startup.

What should happen
I use Application.RequestUserAuthorization immediately before the camera is used.
According to the documentation this is supposed to trigger the permission request.

What actually happens
When the compiled application is started on an iOS device, the permission is requested straight away.
If the permission is denied, it appears that all further calls to Application.RequestUserAuthorization
instantly return (without triggering another request) and the permission remains denied.

I assume that Application.RequestUserAuthorization would work as expected, if the App wouldn’t already request the permission on startup – but we do not actively trigger this request in our code.
So I guess here is my

How do I get rid of the initial Camera permission request?

What could have caused it in the first place?
For all I know, it shouldn’t be the plist-string for the camera permission.
Is it already just the imports of the ArKit libraries?
If not, how cna I even begin to look for a cause?