because it allows you to define the walk behind area by drawing it in which allows you to create the horizontal parts that can also be walked behind.
AGS only supports up to 16 walk behind areas though per scene instead of one per object but I think if we added the ability to draw in the walk behind area in similar fashion to object area for each object then we would have better control over where our characters can walk without having to mess about making sure our characters don't walk too close to certain objects.
VS current walk behind system covers the entire scene object/image/animation whereas AGS system allows you to define certain areas of the scene.
video from around 4:20 mark. It shows that they draw in the walk behind area (masking method) & then set (same as vs) the walk behind center in which the character will start walking behind the masked areas from.
Do you think it would be possible to add? I was planning on writing an email to you, Alex & David with a proper explanation & ideas of how it could be implemented (visual side not the code obviously).