System.dll always included in Android builds?

Unity Engine
,
1

When I build a completely empty project for android, it includes System.dll

yet the bottom of this page implies you can avoid its inclusion.

I wonder could someone tell me what I am missing?

2

Tried an empty project (added 1 empty Test.cs class) with 4.3.1 and System.dll was not included.

Editor.log shows

Struggling with removing references to System.dll from an existing project myself, I found this answer pretty handy (but still no success):
http://answers.unity3d.com/questions/550309/how-to-know-which-code-depends-on-systemdll-in-mon.html