about the function of “Instance Map”

[Elaineok]

I think it's OK to use "CAM" and "Pairwise Affinities" capturing instance segmentation masks.
Because the "Instance Map" purpose is to distinguish instances, and "Pairwise Affinities" also has this function.
And only using these two modules can make the algorithm simple. Can you tell me why "Instance Map" can't be ignored? Thank you for your reply！

As shown in the figure below.