Duhh... I forgot that I knew that. I just assumed that was the equivalent of selecting "default theme" when using WB.
So I built a Windows 10 Pro VM to begin some testing...
What I did NOT realize was that I could "Show Win+X menu when right clicking the start button", and still have Start10 essentially being run, thereby still retaining the native look and functions of Win10 with the exception of the start button.
This gives me a new outlook on using Start10. (Phoon eats a spoonfull of Crow)
I also installed Windowblinds (knowing that there would be issues). What I could NOT make happen is have any type of skin apply to the Windows 10 style start menu.
It would apply just fine to a Win 7 style or modern style start menu, but never a Windows 10 style.
So, back to my original question. .. Is your answer accurate as to how Gef did this? Do you know that for a fact?