When an asmdef has the auto referenced flag set to false and no additional references it will still cause Unity assemblies such as Assembly-CSharp, first pass etc to be compiled even when they no longer have a dependency on the asmdef.

1) Open Project
2) Right click asset file Assets/Asmdef/AsmdefScript.cs and select reimport.
3) Check the Compilation report in the Console, notice that other assemblies have also been rebuilt.