Okay. I have faced a real, capital letters, REAL, corkscrew serve. It looks like top/side. If you counter the spin the way you would with a regular top/side, the ball goes straight down because, that side of the ball is actually backspin and the other side of the ball is topspin. So, I am back to wondering what most people mean by corkscrew. But I know exactly what Michael Lander's corkscrew serve is like. And trying to receive it is not easy. It definitely messes with your instincts because the ball bounces like it is topspin and you touch where you think the outside of the ball is and where you think avoiding the spin is, and you are falling into the trap and facing the heaviest part of the spin.
On a real corkscrew serve, spin avoidance is on the very back of the ball.