Hi. I am Dmitry, and I have successfully reverted my Samsung ATIV S to Wp8 GDR3 as originally described.
So thanks to the author who made an instruction and prepared the files on yandex.disk!
It worked like charm on my Windows 7 VirtualBox with administrator rights and antivirus software switched off. I switched the anti-virus since such has been suggested for Nokia Phoenix flashing exercise.
The way is even more straightforward than the one with Symbian flashing.
First, install the USB driver and switch the phone to Download mode.
Plug it to the PC and see the phone connected as USB Windows phone device in device manager. Then you can work with WP8 SMD binary USB Downloader Ver. 3.47.exe. No need to install, just run from the directory where you saved it. The program will verify the binaries as you open them. It is quite difficult to make a mistake. When the binaries are verified, unplug and plug the phone back to the PC.
You need to see the phone connected to USB Downloader Ver. 3.47.exe! Then choose the options as suggested by the author and press "Start". The flashing exercise will take a while, and, if finished successfully, the phone will reboot automatically, and you see a WP 8 Welcome screen.
Success with reverting, and remember that I take no responsibility if finally you brick your phone.