I support some computers that auto-updated to 10, and everyone with access to them swears they never hit "OK" in the week leading up to that auto-update. Did the EULA just flash up on the screen at 2 AM?
I guess it reboots to Windows 10, but keeps the old installation in "C:\Windows.old". If you then do not agree to the EULA in the Windows 10 setup wizard it rolls back to your old Windows installation.
Definitely a dark pattern, because most users may feel that going back is not possible.
It took me a little while to identify which shared folders were necessary for various programs used by this business. Having figured out how to re-share those folders and confirmed that everything else was still working, however, there wasn't a chance in hell I was going to roll the dice on a "restore" operation. They had work to do that day.
