I did an policy based ugrade install from 14.22 to 15.00. I noticed on several Win 7 and Win 10 desktops, that during install it opens Windows Explorer. One of my users also reported, that it blinked her display as if I would have connected her PC via VNC.
One hour after I distibuted policies, she called me and asked if I'm doing something on her PC and will it last how long. :-) I was not connected to her PC with any VNC.
IMHO, it would be better not to pop-up Windows Explorer windows open during the install.