Most showers I've done go in with a curb. I've always framed or used concrete blocks, covered with tile backer as needed then waterproof with Kerdi, a few time liquid membrane. I've never used Kerdi board to make a curb less shower floor.
The last time I used 1/2" Kerdi board on shower walls, I later wished I had used 5/8" instead. It actually works better to transition to installed drywall. Stiffer too.
I only watched as a bench, (not shower) was built when I attended the workshop at The Ceramic Tile Education Foundation in '09.