What you mean is probably "[C] High Cliff, upperside". Tiled is only able to autotile the [C] part (see [Tileset Parts] and [Autotile] section). The rest of the high cliff, part "[D] High Cliff, cliffside", must be put manually.
This tutorial is using Tiled, hence you should follow exactly it as is to get the result. So please don't skip the [Tileset Parts] section for proper layering too (I know it's long and boring).



















































