Any reason to use so many material_shadow_z1 and material_shadow_z3 files?

[bhuvnesh123]

https://github.com/h6ah4i/android-advancedrecyclerview/tree/develop/example/src/main/res/drawable-nodpi
Inside drawable-nodpi there is material_shadow_z1 and material_shadow_z3 nine patch image for each density.Then inside each density folder there is material_shadow_z1.xml and material_shadow_z3.xml..

Why not just delete the material_shadow_z3.xml and place the material_shadow_z3<-xxx>.9.png in the appropriate drawable folders without the density identifier?
Or better if you can just use a single 9patch png if the image itself is not really density dependent?