Well this has been around everywhere. While any device is running an inplace upgrade of Windows 10 you can use the keyboard combination of Shift+F10 to open an elevated command prompt. You do need physical access to the machine to do this but… yea. For the fun of it I created a new local user and added it to the local admin group. No issues. My thinking is if you have local access then giving yourself elevated rights to login is easy.
Good news Johan Arwidmark has already sorted this issue if you use SCCM