The instructions for the the convertible collars: the Basic Collar, the Turnover Collar and the Two-piece Collar, focus on the construction of the collar around the neckline - it needs to be fit the bodice of the garment.
The outer edges of these convertible collars can be shaped various ways to create a different styleline - e.g. pointed, rounded, high, low, wide, narrow.... and a mixture of these. (This is in comparison to collars where the name includes the shape - if you make the Peter Pan collar with a pointed tip it is no longer a Peter Pan collar, if you make the Eton rounded, it is no longer an Eton collar).
So... the instructions for the Basic, Turnover and Two-piece end with one particular shape, but you can change that collar tip shape to whatever you want.
Here are some examples of ways to vary the collar shape. The white shape is what you end up with at the end of the instructions for these collars, the colored lines indicate other possible ways you can shape them. (There are many other possibilities. You can test this out, limited only by your imagination and taste).